Haven't had my period in months....??

I haven't had my period since the end of February and I know for sure 100% that I am not pregnant...normally I would skip a month in between my periods but I have yet to have one...5 months later... and I am not on any form of birth control anymore, I got off of the shot some time last year. All I get is cramps every once in awhile, major acne breakouts, bloating, aching throughout my body, hormones changing and etc but no period. Can anyone explain or help me understand as to why??