The same thing happened to me when after about 8 years of smoking every day. I thought I was having a heart attack but found out later it was panic. I stopped smoking pot after that and I did start taking xanax (any benzo should help you tho). I took it for about two years, and once I started recognizing the symptoms of the panic, I learned to deal with it and haven't had any panic attacks in about 10 years. I stopped taking the xanax and was alright. I did smoke it one more time about a year after I had initially stopped, and I did panic, but after I popped about 4mg of xanax I was fine in about 20 minutes. The thing is, after that, I knew that (or in my mind I told myself that everytime I smoked pot I would have to go through that, and to me it wasn't worth it. Hope this helps!