Being a "codependent" or "codie" as we call ourselves here, is very difficult to understand. But it can be and if you want to survive your son's addiction, you need to realize what it is and how to overcome it.
You have to admit to yourself that you are powerless to overcome or control HIS addiction and behavior; knowing he is actively "using" is enough; you don't have to find "proof" or play detective to his whereabouts. You also have to realize that he is the captain of his own ship and the consequences of his actions are HIS, not YOURS!
You also need to realize: You cannot control his addiction or addictive behavior; you have to learn to control how much it controls YOU. You have to establish "boundaries" as to where the actions of his behaviors can and mostly, CANNOT cross over into your own life. And you have to realize and establish that YOU have a life that is separate from his and visa versa.
That is about it in a nut shell but knowing all that and doing something about it are two different things. But in time, with practice and with a little help from your "friends", you will be well on your way to your own recovery.
I would also like to suggest that you look into trying to attend a few naranon or alanon meetings in your area. The more you hear esp. up close and personal, the more you will learn.
