Piper I'm very sorry for your situation and the pain it is causing you. I've been cheated on and found out my husband was using a lot of coke and other drugs and had to finally leave him.
It took me a while to get over the shock and figure out my next move. Stick around and keep reading and please keep posting. This part of the forums tends to be a little quiet, but the Friends and Family of alcoholics section has the same problem/different drug and has a lot more activity.
Do you have anyone in real life you can talk to about this, too?Like a pastor or a counselor? Talking about it will help you sort through all the emotions. There are also groups for friends and families of alcoholics/drug users. They could be a good place to go to talk. (AlAnon or Celebrate Recovery)