Hi everyone and welcome Jo,
I'm sorry for your loss, I know, how it feels. My very first pregnancy was a missed mc (I was 32) and I too found out at the 12 week scan. I found that the best way was to try again asap. I think you should definitely go and talk to your GP about your hypothyroidism and TTC, as it can affect both conception and pregnancy.
Talking about mc, while I fell PG last month, and I would be 6 weeks, I know that I've already had a mc. Even before managing to organise an early scan. PG symptoms have faded away by now, even before started properly, and as it was my 7th pregnancy, I know how it feels.
I too, like many of you feel a bit down, I feel that there is nowhere to go from here. While I have 3 children (aged 8, 6, 4), I wanted a last one, but it seems that it is too late. I'm turning 42 in July (I started TTC for my 4th when I turned 40 ). Also, it is likely that my husband will be sent abroad for a whole year (coming home in every 2 months), so that probably will be the end of the matter.
I know, I'm lucky because I'm not childless, but it is hard to come to terms with the fact that this is probably the endgame for me, and there is the lingering sense of loss right now.
Before I'm off to see the midwife today, I'd like to mention, that with this last PG of mine, it took a very long time for us (7 cycles)to conceive, and interestingly enough it coincided with my smear test (which was done just a couple of days before my OV). I'v read anecdotes about how smear test "helped" with falling PG. Have you ever heard this?