I am 23 years old. I have had irregular periods in the past. It occured, at most, in 2 and a half months but not later than that. But that also, has happened probably only 3 or 4 times since I had my very first period at age 13. This time it has been a complete 3 months since I had my last period. I bought a pregnancy test and it was negative.

I think am on the same diet as I used to be. There is no significant change on my weight. I am not depressed about anything, well a little bit of depression is always there but not particularly now. I am healthy as far as I am aware of.

What could be the reason for my irregular period?