Welcome to SR. There is much good support here and a lot of experience.
Your girlfriend is at the starting gate of recovery. Please keep that in mind as you make any commitments. Whether she becomes a recovering addict is yet to be seen. I think most people with experience with addicts will advise you to make no legal commitment such as marriage and also to protect against any having any more children with her during the next two to three years.
As well, you are at the starting gate of codependency recovery. You have much to learn about yourself and about how to set firm boundaries with addicts and about our difficulty distinguishing reality from illusion in relationship with addicts.
It's good you are reaching out. Since she is the mother of your child, you will always be bound in some way to an addict. So it's very good you have begun recovery. It will need to be for life, as you will co-parent with an addict from now on.
Again, welcome.