Ay, totally normal yan sis especially pag ganitong stage na, a few of us felt the same thing, parang ang bigat sa balakang pag nakahiga talaga! The good news is your OB bukas na so you can ask her directly about it, pero usually it's just the weight and position ng baby na nagpapressure. Hoping the ultrasound kahapun goes well and that everything's perfect, sabihin mo lang sa OB bukas ang discomfort mo so she can give you tips para matulog ng komportable, rest well until then mama!