TMI- Constant Diarrhea

I'm 21 weeks and I have diarrhea pretty much every night. Doesn't matter what I eat. I don't even have to eat at all for it to happen. I had it all the time before pregnancy, but

it's got so much worse now that I'm pregnant. (I've never had it checked out by a specialist). And the stomach cramps that come with it are HORRIBLE. Almost comparable to labor, and it extends up under my rib cage. Is there anything I can take that's approved for pregnancy to stop diarrhea and stomach cramps? And has anyone else experienced this?My fiance gets SO mad at me because I stay in the bathroom every night for like 2 hours. I am miserable, guys.