Got a pelvic & transvaginal ultrasound recently, & now have pain in pelvis, & pain when I contract muscles to stop urination. It's also uncomfortable to sit straight up or bend forwards. Thoughts?

UTI after ultrasound. It sounds like you may have either a urinary track infection or urethritis. You should have this checked out if it persists beyond a few days.
Here are some ... What described seems more implying being related with physical activities, which may evolve to either being better or being worse over time. Nonetheless, time will tell. But one question is why pelvic / trans-vaginal ultrasound was ordered. And of course, one has to make sure of no UTI, PID, ability to empty bladder before blaming musculoskeletal pain, which can be confirmed by Hx & physicals.