Well I just did a few stretches and then some sit ups. Now my stomache is hurts on the low left…

Well I just did a few stretches and then some sit ups. Now my stomache is hurts on the low left side. Throbbing a little. Anyone experience something like that. Worked out 2 days ago and that didnt happen. This is my 1st week working out really since my I found out about my daughter who is 2 (actually found out I was pregnant with her because when I did my work out it felt off. Sure enough. same with my 7 month old) lol well I'm wandering if this is just because I havent really worked out in about 3 years or what. I've been working out basically since I was in 11th grade. And I'm 34. So. Beginner again? Lol ugh. I'm so out of shape I guess 🤦‍♀️😳😭😭