She's pregnant

yeah idk... I mean, maybe it's PMS. But I'm a woman and I know when it's PMS so the husband gets a fair warning that I'm just cranky and irritated. (Usually we just end up watching a bad romance movie that I can rip apart with side commentary, so that's fun lol) Anyway, as a grown person, if you are not able to determine why you're feeling a certain way, just staying pissed is not a solution. Either get over yourself and start treating people right who can't help that you're in a bad mood, or really look inside of you and figure out what's going on. "Idk but I'm pissed" is something my 7yo can get away with, because he can't yet fully handle his emotions. I assume your gf is a grown woman, so her standard should be higher than that. So I think you should at least establish that if she can't point out a problem so you can find a constructive solution, she has no right treating you this way. That's not how relationships work, you don't have a partner so you can stomp on them when you're feeling down. Let her sulk and do your own thing instead of waiting for her to snap out of it - that type of behaviour is just manipulative bs and not something a relationship thrives on.