How can I get a copy of my ultrasound report?

Ask your doctor. Your doctor should be able to provide you with a copy or authorize the lab that did the study to send you a copy. Just ask!
Ask for it. This simplest approach is to ask for a copy at your next appointment. Your medical record is owned by the practice; however, the information contained in that record is yours. You have the right to review your record and request copies. A formal request would need to be in writing and there may be an associated charge for the work involved in preparing copies, but it cannot be denied you.