What a total pain! The discovery of the MTHFR gene is fairly recent and there's still a BUNCH of debate about it. Some doctors say it has nothing to do with anything and others think it does.
I had a stroke recently and the only cause they could find for it was the MTHFR mutation. My family history is that everyone has died either of stroke or blood clots, so my family got tested for the gene and, sure enough, every last one of them has it. I am also unable to get pregnant and my GYN seems to think the mutation contributed to that.
I was told (by 2 doctors) to take 800 mcg of folic acid, 1 full-strength aspirin and a daily B-complex and my chances of having another stroke become unlikely. I would suggest you do the same and hopefully you will be able to carry to full-term whether your doctors believe in it or not.
I know personally how devastating it is to not be able to have a baby but have discovered that I can love an adopted child every bit as much as I would a child I conceived. Please don't rule out that option either.
Good luck with everything!