Baby dropped

I'm 33 weeks today and noticed my belly has dropped and I feel pressure in my pelvis when I stand or walk. I went to the ER last night due to dehydration from sudden diarrhea and vomiting that lasted maybe an hour. I had to be given IV fluids and meds to stop contractions. I wasn't dilated when they checked last night but my stomach hadnt dropped either. I dont know if this is connected in any way. It also wasnt a stomach virus like they said because I went home feeling fine eating without feeling sick. My boyfriend and two kids are fine. I think maybe its pregnancy related some how. Thoughts?