Have any of you had health problems after quiting smoking?

I quit smoking 3 months ago and have been plagued with chest pains, panic attacks and the like. I was experiencing some of these problems before I quit, but during that time I was on and off smoking. Have been to dozens of doctors and have had dozens of tests. Nothing is coming back wrong. But this is pretty intense and I would think it would have started to go away by now. Someone told me it can take up to 6 months for people to get back to being "normal". Any one out there was some experiences with this?