Stomachache

Hi I'm 22 weeks pregnant now. Over the past 2 to 3 days, I'm having stomachache diarrhea kind of pain on and off-have been going to toilet as well not exactly diarrhea too. Took charcoal pill once and relieved symptoms. However it's back again. I will feel stomachache on and off. Is this normal for 5 months pregnant? Or is it something wrong I ate? No vomit though.