What could it be?

17 weeks pregnant. I got sick on Friday considered it stomach flu. Had diarrhea and threw up liquids a few times. While that was going on I would get a sharp pain (thought gas) in my stomach every hour or so. Felt like my stomach tightened. It's now Monday morning 3am and the diarrhea and throwing up stopped Saturday night. But I still get this occasional tightening very painful pain around my uterus. It's been a few hours since the last one. I'm just looking for some ideas of what the pain could be. I got to call my ob later today as I was too sick to show up to my appointment Friday and had no phone, so I'll be asking him. And baby is still beating strong I've checked with my Doppler 145-150 bpm.