Uy, please check with your OB ASAP about the discharge and those back/belly pains, better safe than sorry sa ganitong stage, lalo na may conflicting ultrasound dates pa.
The creamy discharge could be normal, pero kailangan lang ma-confirm ng doctor kung okay lang talaga, lalo na kasama ang pain. About those ultrasound differences, itatanong mo rin yan sa doc kasi importante malaman ang actual due date mo para alam ninyo kung ready na talaga. Fingers crossed na malapit na talaga, but let your OB guide you on what's next!