I had this happen at about 17 weeks with my first pregnancy. It is usually when the uterus starts to expand and pushes an adhesion that blocks the intestine. If your pain is manageable and you are able to keep down liquids, you probably don't need the ER right away, but I wouldn't wait too long if this continues. As for what they can do, not much except monitor it, give you some pain meds if you want them, check to be sure the baby is ok. My obstruction lasted about 6 weeks - required 2 weeks in the hospital and eventually resolved without surgery. In some cases, surgery is needed and they want to do it before 24 weeks so make sure you get checked out soon if this continues.
The good news is my first child - Alexander - is now 7 and perfectly healthy. I had another baby 2 1/2 years later and had no issues during the pregnancy and that child - Meghan - is five next month. So, first pregnancy, though a bit stressful, had a good outcome. And, it wasn't so terrible that it scared me off of having another. And the second pregnancy was perfectly normal.