Due to having full blown panic attacks on and off it has stopped me from basic exercise cuz the start of heart racing or breathing fast automatically starts full blown panic attacks. once that slight anxious sensation hits quickly full panicking hits?

Talk to Therapist: It sounds like you need to work with your therapist to do some desensitization therapy or behavior therapy. They can work with you to dissociate the feelings you have with normal exercise from progressing to a panic attack. In the meantime, try an exercise that works your muscles but does not cause heart racing or fast breathing. Walking, weight lifting,

Panic attacks: Anticipatory anxiety. Your brain/ body have now gotten into a pattern of going straight into panic mode, when symptoms that might suggest anxiety are present - even if from another cause. Cognitive behavioral therapy can be very helpful for this. Insure that any medical causes are ruled out. Take care.