Irregular Period After Stopping the Pill

So in December 2015 I went off the pill after being on it for 5 years. I was just too too emotional. My cycle prior to starting the pill was very irregular with months between periods that would last for a few days to a month. The pill made me regular which was a plus. Since going off the pill, I've had my period once in May for 6 days. I haven't had it since and it's very irritating. I took two pregnancy tests and they were both negative. 

Does anyone else have experience with this? How do I make my period regular? While it's nice not worrying about tampons and such, I'm sexually active so getting my period once a month was very comforting.