Clairesmummy- I am so sorry hun We have had really similar experiences, I have also had 3 m/c after having a healthy pg. My last m/c was in august last year, and i had a d&c so that the baby could be tested, because they kept telling me it was the baby had problems, even though they'd never tested them. It turned out that i was pg with a little girl, and there was nothing wrong with her.
All the tests i had done came back normal....except my progesterone level. I am pg again now, 10w atm, and have been taking progesterone pesseries and so far so good. Maybe get your levels looked at???
Im sorry they said just keep trying, it's very hurtful and makes you just want to punch them in the face.
I hope what iv'e shared has helped in some way, and definately go to a FS, they will support you while getting pg, and when you are pg. They may be able to give you answers.
Fly free little angel, and watch over your mummy xoxox