Mama, I'd really encourage you to ring your OB or go to the nearest hospital to get checked today, hindi worth the risk na maghintay pa ng bukas, lalo na at 28 weeks ka na. Better safe than sorry talaga with tummy pain during pregnancy, kahit konti lang ang lakad mo. A few of us moms had similar scares, at iba-iba ang causes, sometimes it's just round ligament pain or Braxton Hicks, pero kailangan talaga ng doctor to rule out anything serious. Seryoso lang, don't wait for your scheduled appointment if you're hurting now, iyong baby's safety comes first. Rooting for you!