18 weeks pregnant, little bit of dark brown spotting yesterday, very full feeling and tightness from constipation and/or growing uterus . One weird, mild cramp , higher up in my stomach for about 15 seconds. Finally had bowel movement last night with ease that relieved pressure and fullness, but no movement from baby since then till almost noon now. No more spotting. Baby had been very active this week. Last week heard heartbeat strong and found quickly. Left msg for dr and now waiting, any advice?