I would put off the wedding for at least a year and see if his actions match his words of promises for recovery..
If you will read through my past posts you will see that living with a drug addict is painful and it doesn't get better, it gets much much worse the longer they use and the longer they stay in denial about their problem.
I've given my Ah chance after chance to straighten up, clean up and be a husband.. I'm now filing for a Divorce next week because I'm sick and tired of being sick and tired and I know in my heart that he's not going to get better..
please please please don't marry this man...