Asking doc for an u/s

I have been going to get my ultrasounds at the high risk doc office but it is with a tech that goes super fast less than 3 mins and less than 5 mins for anatomy scan. My reg doc has an ultrasound in his office but hasn't done one. I would like him to do one for his opinion and my comfort because I also found out I have an anterior placenta and haven't felt my baby move and this is my fourth and I am 21 weeks and 1 day. Does anyone think he will say no and how should I ask him?