Doc considers me to be high risk preg. I have to get 3 vag ultrasounds a week apart from each other. Is this too many? Worried it will harm pregnancy

Family practice . Ultrasound is not x-ray it is perfectly safe for your baby.
OK if careful. Vaginal OB us is a perfectly safe test assuming there is no dilation of the cervix, which can be checked for by performing a pelvic exam. Please ask your doctor what they are worried about /looking for - perhaps it is to check for appropriate growth or the amount of fluid around the fetus.