I think your heart is alright, just let it work and quit thinking about it. Yes, I know it isn't so easy, but nothing in life is easy, just stop thinking about it: believe in yourself and your heart, be optimistic and think positive: start working out lightly, if a bike ride is too much then walk at 4 mph for a mile, then a 1.5 mile... for a few days, you know the routine, work your way up slowly and believe it is RIGHT.
I think your mind is a big, maybe the only, problem you have.
I didn't follow exactly what supplement you were taking and if it was "legal" I doubt it did any damage, and I assume you discussed the supplement with your doctor. If not that would be a good addition to what I say above.
I believe you can do it, and so do you, just get your mind "around it".
Hey thanks alot for the comment. I'm amazed at how helpful this website really is. The supplement I was taking is called N.O. Xplode my doctor doesn't know much about it, only that the Nitric Oxide can cause a chemical imbalance in the brain, and it has a lot of caffeine. But I have been off of it for so long withdrawal should be over. And I know what you mean about taking it slowly and I know you are right, its just so dang hard because my workouts were so intense and strenuous and now I can hardly stand up off the couch without my heart racing and a sense of panic. Thanks for the comment, and advice. It really does mean alot to me.