Welcome Gerette,
My son began his using in his teens also. I wish I had been more aware at a time that I had more say in his privledges.
I too feared that the relationship would suffer when I put my foot down.
Amazingly, it really didn't in the long run.
You might try approaching things with YOUR interests at heart, rather than making his decisions for him.
This means setting the rules of your home, period.
No selling or using drugs.
No using your "appliances" (computer, cell phone, car) to do so
Unfortunately his bad choices have forced you to remove these things from him. You are not taking things away, he lost the priviledge.
By doing things in this manner, you place the chance to make better decisions in his hands.
Should he choose to continue, knowing full well what is lost by doing so, well, it really isn't experimentation is it?
I had to step back and let my son prove to everyone including himself that he had a problem.
Me saying he did didn't matter one bit.
I hope he sees the light
(((Hugs)))
Cece