Reading between the lines here, I suspect he's been shooting up a heck of a lot more than subs. Unfortunatatley, it becomes impossible to believe anythig an addicts says.
Sounds like you may have fallen in love with who he projected and you wanted him to be, a hopeful fantasy. And that's the part you might want to focus on. It was not real, despite how it may have felt. And know you can't fix his addiction.
Take time to grieve the loss of the fantasy and learn from it. Looking back, what signs did you miss? What kept you engaged in the relationship? What can you do differently next time to differentiate between fantasy and reality?
He's just one bad apple. Does not mean the whole orchard has the rot.
Take your time and grieve.