Please try and think with your head, not your heart. Your one and only priorty is your child. That's it.
A child raised in an addicts home is very toxic. You have to be a responsible parent and provide for this child, this cannot be done if your husband is blowing all the money on drugs. This is a simple mathimatical equasion.
As for what you did to make him use...the answer is nothing...he uses because he is an addict...period.
Do whatever that needs to be done to protect your child. As for hubby, this is his problem to resolve, not yours.