Its probably your tummy is stretching to make more room for your growing baby. It does tend to be uncomfortable. But if it gets really bad or you start bleeding call your doc asap. Or just give your ob a quick call to calm your nerves :)
Hi! I'm 15 wks with my 3rd. It sounds like it might just be round ligament pain. It can hurt. Just try to drink plenty of water. If you get tightening and feel really uncomfortable in your belly, it could be braxton hicks, I started having a few around 12 weeks this time, but those aren't painful.
It's pretty normal to have abdominal pains as your belly is stretching to make room. I wouldn't freak out unless you had cramping followed by blood or fluids, not urine.