heart racing

hi, i've had panick attacks for about a year now. and i've had some trouble with my heart and stuff. every month or so i have a big panick attack. The thing is that im not scared at all....my heart goes super fast and it beats really heavily in my chest. I know im not going to die from it but every time i keep having one of these big "episodes" my heart races longer than the last time. The first time i had it, it was only 45 min...then the next was an hour and the next was 2 hours.....and recently its kicked up to 3 hours straight of doing this.....and im calm and everything....i usually can make my heart go as fast or as slow if i think about it ....but i can't seem to get it to go down to normal rate...so im worried if i go to long on this hypertension that my heart will do somthing bad...and im wonering if it has some problem in my neck thats causing it? cause i heard that it might be a problem in the brain stem or somthin....but idunno......the only thing that concerns me is that i might get panick attacks every now and then but when i have these...im not scared at all.....unless it keeps going on and on and onnnnnn....i feel like im about to pass out.........but i don't...so yeah..and no one around here knows how to trigger where im getting my panick attacks, and what the heck im so afraid of. The therapist i went to could only find a bunch of little problems spread out everywhere when we were trying to find the root of the problem. And the problem is becoming more severe...mabey i have to much stress or somthing? cause i have no idea...um yeah thanks for readin this :D