abnormal heart beats

hi, my name is Bosco and i'm 24 years old,ever sincweI could remember, whenever I went to a doctor for any kind of check up, when they check my heart they always show some concern, because of my heart beat rythem and I'v been checked out twice for that by specialist and the results came out normal, but sometimes I cant even feel my pulse and sometimes I can feel my hearts beats slowing down and in those cases I find it hard to breath, I really need some help, if anybody know what might be wrong with me, please help, because this is causing me lots of stress.
thanks

[Jerry_NJ]

Sometime we have the old "chicken and egg" paradox: in this case: is the heart rhythm causing anxiety or is anxiety causing the heart rhythm?

You have most of the answer to this paradox, and the fact you say you feel your heart makes it at least possible that your are obsessing  conscious or unconsciously, and that is the base problem.  This can be tested if you can distract yourself completely enough that you can at some point look back and say "I was not thinking about my heart".   If the rhythm is still a problem you may need to be checked by a 24/7 monitor that you wear for a day or even a couple of weeks.