need help on irregular menstruation

Hi, im Bee. I'm some kinna bothered and in fact kinna scared. Im 23,female,single and I have an irregular menstruation these past 3 months. Im scared. Im really sure that im not pregnant. Im not really use to this problem since I used to have a regular period. It is just by these past 3 months that I was not having my menstruation. Hope anyone could help me with this problem.

bee23