Id also say bloating/gas pains. I get them often enough at 13wks and have been a lot since 8weeks.
Do you get it mostly when walking a fair distance hun, iv had really bad pains on and off while walking that stop when i stop walking then start back up as soon as i start walking again midwife said its the stretching of ligaments in your stomach as you walk
Bloating is the most likely culprit. Try avoiding gas causing foods for a while. The bloating is likely to hang out a while. Hope you feel better soon