Massive hugs. This is the hardest point, hang in there and wishing you all the luck in the world. It does get easier although it remains terrifying. 
I had my DD 8 weeks ago - it was my fourth pregnancy and until they handed her to me, I never fully believed I would have a baby.
The first 12 weeks were hell. Absolute hell. As I’d had two back to back mmcs at 11 and 10 weeks only a few months before this, as well as an earlier miscarriage at 5 weeks, it just felt like Groundhog Day of the worst kind, and I think I had PTSD, as I suffered nightmares and flashbacks. I cried every day. I had bleeding in every pregnancy, including my successful one, which put me on a knife edge.
I’ll be honest, I didn’t get the reassurance I was hoping for from my 12 week scan, it all still felt too fragile, but had a private one at 16 weeks, which helped and then at 20 weeks it got easier when all was well.
At that point, I decided I would do everything I could to enjoy my pregnancy. I told my colleagues and close friends and just did my best to enjoy it wherever I could. I had to fake it a little bit until I really did start to feel positive and happy. I really loved being pregnant in many ways, and apart from the awful history and rough first 12 weeks, I had a lovely, easy pregnancy and felt really well.
I still didn’t buy anything until around 32 weeks, and my nerves got worse again towards the end, but I will still treasure the experience of being pregnant.
Good luck for your scan on Monday. Will be thinking of you.