Hi Lairdoz,
Gosh your situation is so frustrating, it's making me frustrated reading about it, so I can only imagine how YOU feel! I know you've already had one baby, so you know you can carry a baby to term, and this accordingly might sound like a silly suggestion, but have you thought about asking either the old FS or the new FS (I think it sounds like a great idea to get someone fresh to look at your case) to test you for factors that might be preventing implantation? I was just reading this book today that I got out of the library called Getting Pregnant, by Niels H Lauerson and Collette Bouchez, and it had a whole chapter (Ch. 15 - Preventing Miscarriage: Now You Can) discussing ways to counter factors that might prevent, disrupt, or undo implantation. Most of it is stuff that we all already know like taking progesterone during the TWW to maintain the uterine lining, but it also discussed stuff I've seen discussed here but really didn't understand like killer cells and other autoimmune disorders where your body attacks the embryo. The conditions/tests that the book discusses are:

1) a screen for seven antiphospholipid antibodies, which attack the lipids that aid the formation of the placenta and blood vessels (probably not the best test for you since this comes into play AFTER you have an implanted pregnancy, apparently). The treatment is baby aspirin a day during pregnancy, sometimes in conjunction with a low dose of heparin. (Getting Pregnant at 320)

2) antinuclear antibody (ANA), anti-DNA, and antihistone antibody screening: according to the book, these cause inflammatory reactions that can attack the embryo. This is likely, apparently, for people who have a history of inflammatory health problems such as rheumatoid arthritis or lupus. I suspect chronic fatigue syndrome would probably factor in there as well, although the book doesn't mention it. The treatment is anti-inflammatory drugs, including corticosteroids such as prednisone, which I've read about some girls on here taking, often in conjunction with the anticlotting drug heparin. (Getting Pregnant at 321)

3) If you and your husband have similar tissue structure (which apparently is NOT related to similarities in genetic background or anything like that), your body may not produce a substance called a "blocking antibody", which normally turns off your immune system in relation to a pregnancy, preventing your body from attacking the embryo as a foreign object. The test for this is a tissue typing test that determines if your biology is similar to your DH's. If so, a second test, called flow cytometry, helps determine if your body can produce the blocking antibody in relation to him. If not, then the treatment is that you essentially get immunized with a serum made from your DH's white blood cells! (Getting Pregnant at 322)

4) Screen for an overabundance of killer cells: apparently all of your bodies have both "helper" cells and "killer" cells; if there is an overabundance of killer cells, things get out of whack and your body starts killing things that shouldn't be destroyed (like an embryo). The test is called an immunophenotype, which identifies 5 different types of killer cells and the levels of each in relation to helper cells. According to this book (from 2000, so this may be out of date), the best treatment is an intrevenous immunoglobulin (IVIG) treatment, where you get a 3 hour infusion of highly purified immunoglobulin every 28 days until pregnant, up to 4 months, plus mothly treatments after conception. According to the book, "Studies show IVIG works as a kind of fertility "sponge", absorbing the excess killer cells so they can't affect your baby, while enhancing your production of helper cells, which mediate and control what your immune system destroys and what it leaves alone."

The book also notes that some bacterial infections that may be symptomless and sometimes present for months or years can cause infertility or miscarriages, and points out, as I head read elsewhere, that a lot of fertility clinics now routinely prescribe antibiotics for women (and sometimes their partners, too) to take during the cycle and TWW. My clinic didn't do this, but I've read of a lot of clinics, in the States, at least, that have seen success rates go up after introducing the routine use of antibiotics. Maybe you can ask your clinic about taking antibiotics (the book recommends erythromycin, since it is safe in pregnancy) during your next FET.

OK, hopefully none of these issues is affecting you and you'll win the numbers game on your next cycle. But since you're looking to re-evalute your protocol, maybe some of this stuff will help you and your FSes make some headway. BTW, I don't know if the fact that you've already had one child excludes the possibility of your having any of these conditions, but I feel like I've read somewhere that sometimes the delivery of the first child is when the body starts making some of the antibodies. Ask your doctor!

I really really hope this next FET is the one for you.

Kitkat72