Birth control/period help asap

So... I got off my birth control (the pill) in November (2015) I got a period in march the end of march, it is now September 1st. Ive taken multiple pregnancy tests & they've all come back negative. I guess im just scared why I haven't had a period since march. Everyone says it takes a while for bitch control to get out of system but Ive never had this problem before. Has anyone else been through this & can maybe give me some insight? I would love to know. Im starting to get really worried..