Hi, I'm phallophobic and cupiosexual. Its a weird combination to live with considering I'm ace, but i want sex, but I'm afraid of male genitalia. I've had people tell me that this all makes me undesirable for a relationship. Thoughts?
I’m going to assume here that your flavor of cupio means that you’d be interested in a sexual relationship with someone who has a penis?  Because sex doesn’t require a penis to be present, and you might be able to find a partner where you could sidestep the phallophobia entirely.
Anyway, “desirability” is highly subjective.  For some people, that would be an immediate deal breaker.  However, there are lots of things that would be immediate deal breakers for various people.  It would not be a deal breaker for everyone.  Some people would be fine with that.  There’s more to who you are than what you think about someone else with their clothes off.
The key would be to find someone who is patient and understanding and willing to move at your speed. Â A hookup or a one-night-stand would probably not be willing to move at your speed. Â A friend of a friend or someone on a dating site might be.
Going back to the phallophobia, it might be worth looking at why you’re afraid of penises, and if there’s any way you can try to address that.  This is something you can start before you even try to get involved with a partner.
Do you think they’re dirty?  Know that when they’re washed, it’s just skin.  They’re as clean as your hands at that point.
Not a fan of fluids? Â Condoms are designed to keep all that contained.
Not sure what they do? Â Try reading clinical descriptions of arousal, etc. to get a better idea of things. Â You might think of a penis as some sort of uncontrollable organism that acts on its own, but remember that there is a person attached. Â They might not be able to stop it from getting an erection, but they can definitely control what they do with one. Â
Don’t like how they look?  Yeah, they are kinda weird looking, but so are toes.  You also can do things with them without looking at them.
Don’t like what you’ve seen in porn?  Porn is acting.  Sex doesn’t have to be like what they do there.
Afraid you won’t know what to do or won’t do it right?  Ask your partner to describe what they want.
Afraid of pregnancy? Â Learn about and properly use birth control. Â Also, there are activities that have pretty much no risk whatsoever of pregnancy.
Afraid of STDs/STIs/etc?  Have your partner get tested and use condoms to lower the risk.  Learn about how they’re transmitted and take steps to avoid it.
Don’t want to touch one?  Gloves might help.  So might toys.
Afraid of penetration?  There are other things that can be done instead.  And if you’re just not sure what it would feel like (Like if you think it might feel too weird or hurt) and you don’t want to be with someone when you find out, there are all sorts of toys you can buy so you can find out on your own.  (Even Amazon or Drugstore.com sell them.)
Just plain not a fan?  Don’t worry.  You don’t have to be.
And talk to other people who are or were phallophobic and see what they’ve done.  They might have tips you can use.
If you decide that you want to involve a partner, remember that you can go slowly.  It doesn’t have to be zero to full speed instantly.  So start with the basics and take another step when you’re comfortable.  You’ll need a cooperative partner for this, but if you have an uncooperative partner, then that person should not be your partner anyway.
You can plan what you want to do and set parameters ahead of time.  Maybe at first, you can just look at it.  No touching on either end, just looking.  Next time, try touching to get a sense of what it’s like.  Possibly do this in the shower, so you know it’s clean.  Then, if you’re ready, have them get an erection (although likely that would have already happened…).  Then see if they’ll masturbate while you watch.  If you get comfortable with that, have them guide you through the process of stroking.  Eventually, maybe you’ll be willing to try oral or penetration or whatever.  But move at your own speed.  This was just an example, do what’s right for you, not what some random guy on the Internet has to say about it.
It’s also important to know that it is okay to stop at any time.  It is okay to say “No, this is not what I want.” or “This is as far as I’ll go”.  You can even stop after things have begun.
And it’s okay to only be willing to do certain things.  Maybe you discover that you’re fine with X, but not Y.  So do X all you want, but you never have to do Y.  (There’s something called a “Want-Will-Won’t” list that might help here.)
There’s more information along these lines on my site:  http://www.asexualityarchive.com/an-asexuals-guide-to/
It’s not exactly about the intersection of cupiosexuality and phallophobia, but some of the stuff there might be useful.