I too had a MMC in my first pregnancy and found out at the 20 week scan thinking there was nothing wrong- the shock of it is just terrible....and today is just such shit timing for you, isn't it?
I'm not surprised you feel as you do.
Sometimes spotting in PG is not a bad sign, and it is important to remember that women do spot and go on to have healthy babies, but the faint test must also be a worry for you....
Can I suggest something here in case the worst does happen? It might not be the time for suggestions, and might be a bit graphic and if you aren't up to it, skip the rest of my post-
Statistically if you lose the first 3 pregnancies back to back, you are still more likely than not to have a healthy 4th pregnancy....up to 80% of MC are caused by random chromosomal problems not something reoccurring, so the odds are in your favour, although I'm sure it absolutely doesn't feel like that right now.
However, some women do have a problem that is causing the miscarriages, which is why if you have 3 miscarriages in a row they suggest you have some tests done to check that there is nothing wrong. These can include how your blood clots, you (and your DP's) chromosomes etc. The EPU should be able to advise you, or your GP can refer you.
One of the really useful things to do is to test the baby to see if its chromosomes are normal or not- as I say in up to 80% of MC they are not, and the baby would not be viable, but if the baby did turn out to have nothing wrong, this would suggest that there might be another problem interfering with the babies growth such as clotting, killer cells etc which could be treated so you don't lose any more viable ones.
Unfortunately, the way the baby is tested is by sending off the clots for analysis. This means, if you have an ERPC, them saving them during the operation, or (horribly) if you are naturally Miscarrying, saving the clots so they can be tested. For me this unfortunately meant putting a sieve over the loo to catch the clots which I then put in a little pot in the freezer till I could get them to the EPU. I'm sorry there is no delicate way of putting that, and it is a truly horrible thing to contemplate doing......but I'm suggesting it as someone who has been through this a few times now and frankly, nothing is worse than losing another one, so I'd rather know in case it can help prevent that.
I still have everything crossed for you that the worst has not happened this time for you, though.