Sorry no advice but am in almost the exact same position. 14 weeks with uterine prolapse from previous birth- although my birth was "easy" with just gas and air. For various reasons I've not even seen (or spoken to) a midwife yet, and not sure what, if any advice I'll get.
I don't have a grade for my prolapse - it was looked at by a physio who just said it wasn't too bad/ was 'manageable', but that as I'd seen her first thing in the morning, ie, hadn't been on my feet all day, that it was just what she could see at the time. Mine also isn't reversible with pelvic floor exercises but they may help, so I'm cranking those up.
In the last week I've just started feeling it more and am trying not to pick up my toddler too much (impossible!), and even short walks are making it worse (really not good for my fitness levels).
All I've found from googling is people saying that doctors told them to come back when they were done having children, but not what to do while carrying a whole heavy baby inside you! Oh and a couple of scary articles about miscarriage that I'm just ignoring.
If I get any answers when I eventually see a midwife, I'll update you with what they say. The only thing keeping me positive is that it seems prolapses are very common, just not often talked about, and so there must be many many women going through pregnancies with existing prolapses.
Have you thought about seeing a private gynae physio? I did after my 1st and found it really helpful. I hadn't thought of it while pregnant, but having felt my prolapse a lot worse this last week, I might see about making an appointment with her again. So much more knowledgeable than a midwife or GP. My last appointment was somewhere between £50-£80.
Good luck with it.