When I have sex, I seem to get my period the very next day or shortly after. It happens often, so I'm a bit concerned now. I also have an IUD, so I'm assuming it's linked. Because of my IUD (Skyla), my cycle is already so irregular. I honestly don't know what to make of this. Maybe it's just a coincidence, but maybe not. There's nothing else going on that makes me worry that something might be wrong.