Weird feeling.

Dear husband and I had sex tonight for the first time in about three weeks. I came and we took a min for me to catch my breath and when we started up again a different position you lower stomach started to cramp up, pretty painful. It surprised me and I made us stop. Doggie style was the only way I could let him finish. Had thi weird pain/feeling ever happened to anyone else? I'm almost 16 weeks. I'm not bleeding or anything...the feeling went all across my Lower stomach too...like in a line about an inch or two below belly button...