I'm feeling a type of fullness in the pelvic area, but no pain. this is the second day. i did an ultrasound a few days ago and it was normal. what could be causing this & should i get worried?

Did the discomfort follow menstruation, intercourse,strenuous physical activity? These are some causes of pelvic congestion which is difficult to see on an ultrasound. If you haven't had a rectopelvic examination by a gynecologist, I strongly recommend one. If symptoms persist,an MRI or CT scan would give a more complete picture of the pelvis but I would leave the decision up to the gynecologist.