Hello twentysomething and welcome to SR. It's good to have you with us.
I can understand you feeling scared about this. Facing any addiction is hard, even if you've done it before.
You probably need to speak to your doctor about this and get some medical advice. I have no experience of drugs to help, though I'm sure others will be along shortly to share their experiences.
Congratulations on the 5 years heroin free by the way, that is fantastic!! X