I'm so sorry OP, I remember the days of wondering whether I would ever be a mum, also in my 30s and the clock was ticking away!
I had a MMC at 12 weeks which had developed until 9 weeks followed by one at 9 weeks, not sure how far along I had got.
I asked my GP if they could do any basic blood tests - which they did. This flagged a potential problem and they did refer me to the recurrent miscarriage clinic. This was covid times and the waits were long so my husband and I decided to see someone privately. He felt my thyroid function was too high to support a pregnancy (different to what the GP had spotted) and got it under control and then told me to try again.
Once pregnant I was prescribed asprin, heparin, progestrogen and levothyroxine and carried by daughter to term, she is now 2. Currently 31 weeks pregnant again, saw the same Dr and followed the same routine and no complications.
Ended up being 2 years from getting pregnant the very first time to giving birth to my daughter and I spent a lot of that time very anxious.
If you can afford it, I would really recommend paying to see a specialist but asking GP to do basic bloods first (blood clotting disorders and general checks). I live in London and we have probably spent £8k altogether for both kids but this included extra scans, harmony tests and I needed some fertility tests before this pregnancy which soon added up.
Appreciate this is a lot of money and out of reach for some people but even paying £250 for one private consultation might point you in the right direction.
I know it isn't much comfort but I was told over and over again that two in a row does not increase your risk of a third, most women find no issue but go on to have a healthy baby next time.
Would recommend the books 'Coming to Term' and 'Pregnancy After Loss' (this one for your next pregnancy)