As soon as you get your next BFP, ask them to first do a set of quantative hcg beta blood tests to see if your levels are rising at the appropriate rate...and also mention that you would like an early reassurance scan between 7 and 8 weeks, as you've had a missed miscarriage. If they WON'T do this for you, it's probably time to find someone else WHO WILL!
Those of us who've gone through losses need all of the reassurance we can get, and any doctor that doesn't understand that should probably go into a new profession, IMO.