What Causes Rapid Heart Rate And Palpitations?

Hi, I am a 41yr old bulimic male for many years, otherwise generally fit and exercise regularly. I got diagnosed with BPV 4 months ago after having gone in to A&E and actually passing out, in and out of hospital over 2 weeks and various tests. Anyway 4 months down the line having recovered from the BPV, I now struggle to do the distances (running)and intensity of exercise that I used to do. I woke last week with really mad racing heart to the point where I felt I was going to pass out again but didnt have the nausea and dizzyness like with the BPV previously. Thing is, I get palpitations pretty much regularly, not to the point where I feel like I am going to pass out though anyway, called the ambulance out who did ECG and didnt find anything wrong with my heart, saw my doc next day who also did ECG same result no heart problems. He is now talking about holter monitor and thyroid checks because of the palpitations. I have stopped all cafeinated drinks ie coffee and coke, cut out sugars and chocolates altogether and havent purged now for over a week. Palpitations seem to have disappeared and I feel so much healthier. Is this possibly the cause of the palpitations and am I wasting my docs time by going ahead with the tests and holter monitor? Also having read up on bulimia symptoms cures etc are there any tests that can be done to see if I have done any irreparable damage to any internal organs and is full recovery possible?