I personally am taking progesterone cream called Pro-Gest... prescribed by my doctor but you can get it online.
It has worked awesome for me and I like that it doesn't have any weird symptoms to go along with it, unlike the suppositories. My doctor told me that she doesn't put people on suppositories because, for some reason, progesterone in the form of a pill doesn't absorb in the body well and actually turns into something harmful in the body once it is digested. So, that's why she put me on the cream.
I was worried about low progesterone too, but I am now almost 12 weeks preggo and doing great.
Don't worry about what the doctors say. If you're meant to have a baby, you will. Babies are able to undergo a lot more than we think. I was told for a year that it would be hard for me to have kids, and now here I am.
Be excited that you're pregnant and enjoy this time. I know what it's like to worry, but try not to. It's a really fun time :)
Congrats by the way