Could be anything from heartburn to gallbladder to preeclampsia. I would check with the Dr to make sure.
Also try tums. I find it helps. I get almost like a heartburn feeling under my ribs. It's them growing hair. But if it doesnt help contact your doctor.
That can be a lot of things. It would help to know how far along you are. I would call the Dr. It could be nothing or something serious. I'd rather be safe than sorry and get checked out.
What side? I have it on the right and it's my gallbladder.