I would take your doctor really seriously. I don't think he would tell you to quit right away if it was not a serious situation. Like Surrendered said, you never know where the point of no return might be. I think we all understand how overwhelming the thought of quitting forever is, but we all also know of people who didn't quit in time and lost their lives because of it. I had a close friend who didn't make it. Not trying to be super negative here, just telling you what's at stake, for real. Please quit.