need help

[Ronald Marin]

I would like to know, if any of you could help out on determining my
problem. It has been a while know that I feel very bad for no reason, I feel
space out like I am not in myself, if I do moderate exercise I feel worse,
my heart pound rapidly and feel very week. I am 36 years old, quite smoking
one year ago, eat healthy. Doctors don't do any testing to my head, they
believe I suffer of panic attacks, but I don't think so. Sometimes I believe
I will go crazy, what should I do?