28 weeks prego with chest and abdominal pain?

i just turned 28 weeks today and since i got up this morning i been havin pretty bad pain in my upper abdomin lower chest region. like under my boobs around my lower ribs. does neone no why this is happening? if its serious? or how i can make it stop. i cant call my doc cuz is saturday there closedand im at work so i dnt wanna leave unless it could b serious cuz i def would go to thw hospital. any opinions please?