Missed periods. (Really personal and really long)

Ruby • Just a girl obsessed with death and the paranormal.
So I guess I can be honest here. (I'm 15 almost 16 btw) So basically when I was a month old I had an ovary removed, because (what my mom said) I had a small tumor so it had to be removed. It was removed the doctor said I was fine to have children in the future everything was fine i would have a normal life with just a single ovary and I guess i could say he was right. When I was 11 I got my period it was pretty normal month to month menstruation but then it started becoming irregular. I think I was maybe 13 when I started missing my period and it wasn't 2-3 weeks late it was 2-3 months late. My mom was worried I was worried we both knew I wasn't pregnant (I was still seeing my pediatrician) he said I was fine. So flash forward 3 years later (I now have an "adult" Doctor) after what he said my periods became somewhat regular I guess but the downside to that was I had extremely painful cramps they were so bad I had to miss 4 days of school each time it rolled around. So after writing this whole essay I want to cut to the chase the last time I got my period was on September 8, 2014 it is now September 28, 2015 has anyone else experienced this or is currently experiencing this I would really like to know how you dealt or are dealing with this situation.