Palpitations are simply an awareness of ones own heart beating, they are generally a benign variation of normal and do not usually represent pathology. They are commonly made worse by stress
Palpitations can however, occasionally represent an underlying heart problem. A simple 24 hour ECG and a few other tests will exclude this though.
You need to sort out your panic episodes and this problem will resolve along with it. CBT (Cognitive Behavioural Therapy) has a 70% success rate is curing anxieties and phobias. Make an appointment to see your Doctor and he will refer you.