I've been having a period for the last 2 and a half years every 2 to 3 months could u please put my mind at rest.?

Metrorrhagia: I think that what you're talking about is called "metrorrhagia", which just means that the time of your periods is off, but not the amount of flow ("menorrhagia"); if you have both it is "menometrorrhagia"). The most common cause of irregular periods is stress. Obesity can be a factor, as can excessive exercise (like marathoners), and anorexia nervosa. I think you'll have to see an md to sort out.