Mommy, please have this checked with your OB as soon as you can, abdominal pain sa pregnancy, kahit saan, dapat sure tayo na okay lang. Hindi kami dapat mag-assume, lalo na yan sensitive time pa lang ng 18 weeks mo. A few of us moms in my circle had similar concerns, at ang best advice talaga is to get it confirmed by your doctor para ma-ease ang mind mo. Sending you hugs, sis, better safe than sorry!