Sorry sweet, should have suggested this, try and keep a note of what you are doing when you get this pain and dates, times etc. You can take this to the doctor and it might help him form a picture of what the problem is. Take care.
Try not to worry about it. I would suggest you go and see your doctor, if only to stop you worrying and to put your mind at rest. If you get any shortness of breath, dizzyness, sweating or nausea with the pain then pop yourself to your nearest A&E or call an ambulance.