I never get my periods I'm 18 what is wrong?

I started when I was like 12 and have never been regular. my last one was in september but I got it 3 months in a row june july and september 30 days apart abut 5 exactly about 5 days long each then I had random bleeding in october and not again since then. I sometimes get sharp pains down by my hips but it could be gas or something. Whats wrong and what do I need to do to fix it? taking pills are not an option for me.