Forget The Doctor, Go Fetch A Priest

Ghosts

Things that exist in Scooby-Doo:

Jetpacks

Aliens

Instant Hypnosis

Machines that put you in the computer

Realistic hologram technology

Were-Cats

Meteors made of Gold

Self-Aware AI

Underground Egypt Cult

Cthulhu

Soul-Sucking Triangles

Transylvania, PA

Moon Resort

Magical Space Guardians

Transgender Potion

Courage the Cowardly Dog

Warlocks

back of the head scratch

a character shaking their head in disbelief or disgust with hand on their forehead, looking down

that kiss animation used since origins and in every mass effect game where they very slowly go in, hesitate, bop their heads around, and really go in for the kiss 

when a character, usually female, talks and puts their two hands in front of them like a robot and shakes them to illustrate their point

a character leans back on one leg with their arms loose

the exit-stage-right an NPC does after a conversation ends

angry limp wrist pointing

neck/collar bone scratch 

a slow crossing of the arms in times of suspicion

that punch animation 

drinking alcohol and violently shaking head

a character gives a half smile with an eyebrow raised

Deltarune Fun Fact:

At the end of Onionsan's conversation in Chapter 2, they will ask you to come back tomorrow to learn about the music they hears from the lake. However, they don't appear in Chapter 4. The player is told not to expect Onionsan to appear this chapter, both from Susie saying "your weird friend is busy today" and the strange bird-like NPC from the library saying "don't wait". Then in Chapter 5 you can find this same NPC serving "fried dough balls", which Susie says taste like onion.

The answer is: the uterus isn't what causes your period, it is effected by your period. What causes your period and what causes trans women's periods is the same thing: the endocrine system.

HRT changes the sex of your endocrine system. Feminizing HRT makes it a female endocrine system, giving us a 28-day hormone cycle just like cis women. At the end of that cycle, the hypothalamus floods the body with prostaglandins. Those are what cause all but one of the period symptoms, because they make muscles inflame and contract. They are what make the uterus shed its lining, they are what cause intestinal cramps, they are what cause body aches, they are what cause headaches and migraines. The only period symptom not causes by the release of prostaglandins throughout the body is depression, and that is caused by your endocrine system simply not processing as much estrogen and from simply feeling like shit.

So, the only symptoms trans women don't get every 28 days is menstrual cramps, because yes we do not menstruate since we don't have uteruses. But migraines, depression, body aches, intestinal cramps, and the infamous "period shits" don't exactly add up to us having any better of a time. Except we have to pretend that we're fine and nothing is different because no one believes that we get periods, not even cis women.