Welcome KittenMittens. I also have no experience with heroin addiction. However, 3 days clean sounds like a great start.
One foot in front of the other is what you need to do. Keep moving forward.
Shame is normal but there is really no need to feel ashamed about what is a serious affliction. Moreover, you are trying your best to do something about it. Ditch the shame. Be positive and proud about what you are achieving.
You have a support group, and if you feel a connection with them already, then I would really encourage you to go to a meeting and be as open and honest as you can. Addicts understand the terror, the guilt and the remorse. We have lived it in our various ways. This will give you more support to keep you moving forward and rebuilding your life.