Abdominal pain? Gas?

Christina
Hey ladies! I'm eight almost 9 weeks and after a light work out (bike for 30 mins) I get terrible pains in my stomach and lower back. It's not immediately after the gym, sometimes it's an hour or two hours later. I can't tell if it's my uterus stretching, I'm oddly dehydrated, or I'm constipated or something? Anyone else have soemthing similar?