Hi. You may have poked your cervix is my best guess. There is often a discomfort or bit of pain even when it is inserted. That's pretty common. Your baby is well insulated! I would try not to worry. since you posted this, have you connected with your doctor? Why did you have the ultrasound if I may ask. There is really no risk from having this done. https://www.webmd.com/women/what-is-a-pelvic-ultrasound