What's wrong with me ?

I have a question for whoever response... Ok well I'm 26 I have two kids already and I want another baby in the future I'm not planning to have one at the moment but if it happens I'm okay with it because I'm also not prevented it. Me and my husband haven't used protection in a really long time and before I used to be on birth control maybe like 3 or 4 years ago but stop using them because I felt like I was gaining weight. Well my periods always been irregular and never got them when I was supposed too... That's why when I wouldn't get my period I thought something was wrong with me or I was pregnant  back then I was, but like nowadays like the really last time I could remember having a period was back in sept or oct 2014 and let me remind you were still having unprotected sex and i still haven't gotten my period and I already taken like 3 pregnancy test and they all show negative :/ so I'm confused like what's wrong with me ??