Irregular Heart, Pulse Beat, Chest Pain, Tingling In Arms. Reason For Above Symptoms?

Hi, I am 23, female, low to normal blood pressure and a healthy weight. Over the past 6 months my heart beat felt odd now and then, I d check my pulse and it felt as if it beats normally then there is a longer gap between the next beat, then it beats normally again. It only occurs at rest, or when I am really tired (I gave up caffeine but it didn t help). Now for the past 2 weeks I have been getting really sharp pain on the left side of my chest , almost as if it feels heavy and restricted, and my left arm goes tingly (pins and needles), I thought it could be all in my head, but last night, the pain woke me up and I couldn t sleep. I get it when sitting down or walking, it s worst at rest I find. I m far too young for angina? but this is really worrying me now, I went to the doctor and he said blood pressure and heart beat is normal. Any help would be greatly appreciated, thanks.