What Causes Irregular Periods With Less Bleeding?

hello :) my name is Eva and i have a period problem. My period is going a bit haywire and i want to know the cause. I ve been through a lot of things with my period, from flowing heavily, to not seeing a thing. I am one of the few that can say i enjoy having my period. When i was younger (about 10-13) i used to see my period full and heavy and i liked it like that. Now, i see it very little or none at all. i would go without seeing it for two or three, maybe even four months. when it did come, it lasted for two days and was very light. Now, it no longer flows. I only see little of it when i wipe but none on my pad. I m very worried...please help me. I m 18 :)