Are you on any medication? such as beta blockers?
A cardiologist I was under last year had the brain wave of doubling my dosage twice to try and reduce angina. My pulse was down to 29 and 23 when asleep, setting off all the alarms every night.
The anxiety of worrying about it is probably affecting your breathing, you are possibly also bradicardic which simply means that you have a low heart rate, this is actually a good thing it suggests a strong heart because it can get blood around your body in less beats, if it is really low though it can have some side effects i suggest you see your GP and more importantly stop worrying because the breathing sounds like it is more to do with your anxiety then anything else. Exercise will help both these problems
and also i dont excercise and like right now i cant get out two words without feeling out of breath i do have anxiety real bad to