@itssquidstella I see re the follicles, this might be why they want to do AMH, that's fair enough. Although if you got pregnant twice already, I'd think you'll be totally fine from this point of view.
APS (the sticky blood syndrome) would be one of the usual tests, but as you say it's been excluded in your case already. You should probably have Factor V-Leiden, thyroid (all tests, I think there's two different ones), lupus, karyotype, hormone levels (which seems is what you'll be having, to test hormone levels), womb structure ultrasound and HyCoSy, possibly laparoscopy too to check for any womb abnormalities, endometriosis etc.
NK Cells is a looping topic! In short it's a fairly new research in miscarriage and recurrent miscarriage. The theory behind is that Natural Killer Cells which we all have in our bodies and which normally protect us from infections, fight off cancer etc. start acting funny at the beginning of the pregnancy. It's worth noting the NK Cells in our uterus are slightly different to NK Cells in the rest of our body and usuaetheir primary role is to protect the pregnancy. What doctors think happens sometimes is an immune system disorder whereby theose NK Cells somehow think that the fertilised egg/embryo is the enemy and the pregnancy cannot progress as a result. This is what they think happens when NK Cells incorrectly get overly aggressive. Alternatively, they multiple at an increased rate (which is what the doctors think happens to women who have low or no stem cells in their womb) and their levels are too high which in combination with low stem cells leads to holes in the endometrium which ultimately collapses on itself and the pregnancy doesn't progress. That's in summary, it's a very complex (and fascinating) theory and there a lot of voices in support of this theory and lots of success stories once women were treated correctly.
NK Cells can be tested by way of a biopsy from your cervix (this is currently done in Coventry (Prof Quenby and Dr Brosens) and in Bristol (at BCRM). The specialists in Coventry have been researching this for Tommy's for years now. They can also be tested by way of blood tests in London (Dr Shehata). There is some controversy over which method is better, pros and cons of each. Then there are still some question marks over when the treatment should be started, from ovulation or BFP. But as a general rule, if you're diagnosed with it, you're put on low-dose steroids to manage the level/aggressiveness of NK Cells (eg prednisolone) or the more expensive method used by Dr Shehata are IV lipids. Again, there are success stories on either approach, it's too soon to tell which one works better, but indeed, it seems the researchers are on the right track and it might explain why many miscarriages happen.
To make this more complicated, NK Cells levels vary naturally from cycle to cycle - that's why some women may well have a successful pregnancy if they randomly conceive in a lucky cycle, without any treatment.
It seems there is a very good chance of ending up with a baby if you suffer from it, might just need a bit of help. Also it's important to avoid stress - there is a question mark over whether stress is a symptom of NK Cells going into overdrive or whether they might go into overdrive as part of our bodies stress response. So a big chill pill which I'm reminding myself of every day. It certainly helps to stay calm anyway!
Sorry that was an essay, but there's no easy way of explaining this. There's lots online and if you have any questions, fire away as I am just about to start the testing process.