About 3 weeks ago I did some stomach crunches one night. It was the first time I had done stomach crunches in many months, and even then, it has been years since I have exercised on a consisten basis. I remembe being sore the days after, but since then, I have been getting some muscle twitching in my lower abdomen , mainly on the left side, although the whole area, left to right seems a little tight. Did I pull a muscle or strain? However, I tried protected anal sex about 2 weeks prior to those stomach crunches. Could the abdomen pain be related to that? It was my first time.