Pain when walking

Today I've just recently started feeling some pains when I'm walking. I can walk a few feet and then I start getting a stitch like feeling in my stomach/under my hanging belly (I was already obese before becoming pregnant😭)/in my belt line area, I'm not sure exactly where because I can't pin point it. I was wondering if anyone knew what it could be and if I should worry because I'm currently 21 weeks pregnant.