he has gay ocd

I think for large chunks of his life, he's high-functioning enough and so driven by self-consciousness that he manages his OCD well enough to hide it even from himself because it doesn't visibly take up enough time to disrupt normal life. As soon as he notices one of his compulsions being noticed and drawing judgment by others, he alters the behavior to be smaller, but the obseession-compulsion program is still running in his brain and taking up energy and time.

Lots of symmetry OCD, intrusive memories/thoughts, trichotillomania.

Like, maybe when he was ten while walking down a corridor in the Temple with his friends, one of them asked what he was doing and he realized his friends were waiting and staring at him. And he realizes that he's gone back three times to walk over the same tile because he stepped on a crack and he has to set his feet perfectly evenly within the tile now before he can move on, but he is also self-aware and insecure enough to realize that this is absurd. So he doesn't tell them. He clenches his fists with symmetrical pressure until they feel even instead and decides it will have to do even though he still feels the urge to fix his steps. But his friends don't notice he's being weird if he just squeezes his fists instead so that becomes his new ritual for when he steps on a crack. And he doesn't even really realize it aside from judging himself for being so fucking weird.

The name "Anakin" becomes a ritual for him. He has to say it so much, and at the beginning, he can't get the syllables to feel right in his mouth. He refrains from muttering it out loud, because that's weird, but he shapes his tongue/the interior of his mouth around the syllables repeatedly before saying it out loud and then after, too, until it feels right. He ends up saying it so much that he becomes a master of saying it the way that feels right. He says it the same way every time, equal time on all three syllables, first syllable stressed to offset the softness of the last syllable. It becomes his favorite word to say because it's a ritual he can complete and no longer takes up inordinate amounts of time.

Does this with bits of the Code, too. Will answer intrusive thoughts about what an angry, violent person he is with "There is no passion, there is serenity." But he has to say it perfectly evenly in his head. It takes dozens of tries to get it right, all in his head.

He had a thing about swinging his lightsaber an equal number of times (or until there's an equal nebulous weight-feeling) to right and left. The only OCD behavior Qui-Gon ever noticed, because it ate up some of their training time. He mentioned it. Obi-Wan immediately stopped. Started shifting his grip on the hilt evenly between his two hands instead, back and forth, forth and back.

Anakin notices this. Asks. Obi-Wan has to think hard to remember why, but he hates withholding information from Anakin. Ultimately, he honestly tells him he doesn't know why, it just feels wrong if he doesn't. I think Anakin is the only person close enough to ever be curious about any of this and ask further questions from a place of wanting to understand.

He grows a beard out because pulling head-hairs is too obvious, unprofessional, and feminine. Scratching a beard actually makes you look like you know what you're doing (even when you DON'T even know that what you're doing is half-consciously looking for that one perfectly textured and sharp hair-of-the-day to run your finger over and then let go of, catch and release.)

Not a head-canon, but there's a bit in Master & Apprentice where he tugs "nervously at his Padawan braid," then stops himself mid-tug because it "was a bad habit he wanted to break." He then proceeds to stroke his beard for the rest of eternity, especially in moments of uncertainty or stress.

So many intrusive thoughts about turning dark side. (Again, in books, has been known to just bring up this fear out of the blue.) He'll be trying to study Old Alderaanian texts or something, and he'll suddenly be attacked by a memory of that one time he snarked back at some bully instead of turning the other cheek. He'll replay the memory on a loop trying to find a clue that it meant he was going dark, or to Solve The Puzzle of what the Good Thing to do would have been to make that past, long-gone situation go better. Of course, if he told literally anybody (except maybe Qui-Gon who is fucked up about such things) that he was worried about going dark, they would be like "what the fuck are you talking about bro." And he doesn't even realize he hasn't made it past a page of Old Alderaanian text for the past fifteen minutes because he's been stuck on this puzzle until he looks up at the chrono and then berates himself for wasting time, what a Bad Person thing to do.

Textually: The amount of time he spends in the books repeating phrases as reminders or to analyze numerous potential solutions to past events is a big part of why I headcanon him as having OCD. Or rather, it's the ease and comfort with which he accepts this as a valid use of time. It's the way he is used to his brain functioning. He's never like, "Geez, why am I dwelling on this?" the way another character might, the way Qui-Gon does.

Meditation helps reduce his symptoms. They get better at times when he is better at meditating. I guess they call that getting in touch with the "Living Force" or whatever.

His symptoms get worse on Tatooine. His distress makes his obsessions seem "reasonable" because his brain has evidence now that he fucked up. Plus, he doesn't need to curtail his compulsions because there's no one around to witness him. He has worn down grooves in that cave with specific patterns of steps he goes over again and again until they're right. He spends hours a day bombarded with invasive memories of Bad Things he did that led to Anakin's ruin. Things like leaving his hand on Anakin's shoulder one second too long that one time. Maybe if he had lifted his hand just a second earlier. Or left it a second longer and turned it into a shake. Maybe if he replays the memory enough times he can Solve The Puzzle.

His sexuality fits into his OCD in the way that all self-hating gay people with the usual, legacy-variety fears of being a Predatory Gay will use whatever tools they have in their mental arsenal to self-recriminate. He pays more attention than most people to his own sexuality because it is a Different sexuality, and one that comes with fears of corrupting others. Laminates nicely onto fears of turning dark and hurting others. His OCD loves it all, will take all the food.

He has Gay OCD because he is Gay and therefore his OCD is, too :)

If Darth Vader kept him in subspace constantly then he would be cured :))

None of this is medical advice. I am not a clinician. I just have OCD and relate more to the way Obi-Wan Kenobi's mind works than I can say for almost any other character in my 30+ years of reading books.