I would ABSOLUTELY switch doctors! I have switched twice now for the same reason. And something I've learned just recently, quit reading things online! They will make you worry and panic for no reason at all, trust me!
And sometimes doctors/nurses just aren't very thorough... My nurse called Thursday to tell me my hcg levels dropped about 40,000 so she thought I was miscarrying. What she FAILED to do though, was check to see how far along I am (12 weeks today), and realize the placenta takes over at this stage so its perfectly normal for numbers to drop.
I know its so hard, I've been reassured so many times this pregnancy that everything is fine, but I cannot for the life of me be as excited as I want to be for fear of losing this one too...
But the way someone else on here explained to me, even if you let yourself get excited or not, if you do miscarry its going to hurt either way. So at least show you babe a little bit of love, give it a fighting chance.
I sure hope everything works out for you dear. And, if all else fails, go into the ER and tell them you're having cramping (even if you're not), explain your history, and see if they'll do a check. Even just for a piece of mind! That's what I did after the call I got on Thursday and she wouldn't see me until Monday! (Today).