Oo, marami sa amin nagpaultrasound kahit hindi nire-recommend ng OB kasi gusto lang talaga malaman ang baby, lalo na if may unusual symptoms! Ang paninigas ng tiyan at pananakit ay common pa naman sa 33 weeks (Braxton Hicks yan usually), pero since you're worried and you've already been checked by your OB, I'd say go ahead and get that ultrasound for peace of mind, better kami matulog ng mahimbing knowing baby is okay, diba? One of my mum friends did the same thing at 32 weeks dahil sa frequent contractions, and nakita nila lang na normal lang lahat, so she felt relieved na. Just make sure you're really resting and hydrating well in the meantime, at if the pains get worse or you see any spotting, go straight to your OB or hospital na.