Abdominal fluttering/twitches?

Hi all! I've got an interesting question. Over the past couple weeks, I've had off and on fluttering in my stomach, usually in the lower left quadrant. I was so certain I was pregnant at first, because it felt remarkably similar, but two home tests and an office test later revealed no baby.

I've been strength training for a while and started SL Monday. The fluttering has been more prevalent tonight. I read somewhere that it could be irregular firing of neurons, possibly from weight training. Is there any correlation, and has anyone else experienced this? Thanks!