Oh bless you, I am so sorry for your loss.
Your partner is trying to be positive as I guess its his way of coping with it and maybe he feels he needs to be to try and keep that positivity for you.
My DH and I went through a similar thing and it was a surprise pregnancy as I was on the pill but we were very excited. We told our friends and family and everyone was so happy for us and our parents exciting to be having a grandchild and its heartbreaking. You feel you have to cope with their loss as much as your own and you feel guilty getting their hopes up only to dash them.
But I promise you this is no-one's fault. As crap as it is these things just happen.
It feels raw and painful right now as its fresh and it will take sometime for you to grieve this loss. You are grieving the loss of your baby and of what could of, and should have been. All those little thoughts where you look into your future and see a child, that you allowed yourself to feel excited for, have gone. Its devastating.
If this does go wrong and you get confirmation of miscarriage, please talk to one another about it. Its vital that you both try and talk about how you feel. To each other, if you can, but if not then to family and friends to begin with. Don't bottle up how hurt and heartbroken you feel. Take time together, alone, in your own bubble and cuddle, talk, cry, and allow yourself to feel what you feel. You will get through it together, one day at a time.
I promise you will get through this, even though it doesn't feel this way right now.
In time, when you feel ready, you can try again if you want to.
Someone wrote in a card to me when I lost my baby 'The sun will shine again one day' and I remember at the time thinking 'No it never will'
But it did.
I went on to have a healthy viable pregnancy a few months later and that 'baby' is now 20 years old.
Please be kind to yourself. xx