Totally agree with Annie Brooke. That's the first thing that jumped out at me when I read your post. There is absolutely no way that could be true. Do some research on how twins happen and you will see for yourself.
If you are miscarrying, heavy bleeding will happen soon, along with your cramps. But it is entirely possible that you are not, since cramps are a fairly normal part of early pregancy.
Best wishes to you. And sounds like you need a new bf. : [
Identical twins are just a fluke of the egg. Fraternals can run in the family, but identicals do not. There is no way your stupid doctor is correct in telling you such a ridiculous thing as every other pregnancy would be identical twins.
There is no natural way to find out if you are miscarrying without going to the doctor unless you have an ultrasound machine. you can go out and buy a doppler but this early in the pregnancy, a lot of people can't find a heart beat with a doppler anyway. have you been having any bleeding? that would be something to look for. either way, call your doctor, maybe they can move you up faster for an ultrasound. also, how does your doctor know when you will and won't have twins? that sounds pretty silly.. he cannot predict the future, i am pretty sure there is no way to just tell someone every other pregnancy will be twins, identical at that. i'd find another doctor! good luck.