Need good advise! Missed two periods..

I am very confused on what's going on with my body the past month or so. I was on the depo shot for about five or six years then I stopped getting the shot around June 2014. I did this because I wanted my body to get normal again sense it was a long time with no periods. My periods where very regular maybe off by a day or two. Well now I haven't had a period sense December 5th 2014 which was a pretty late period for November, but now I haven't had one sense then. Me and my boyfriend don't use both control or condoms or anything like that sense December 2015. Lately my breast have been really sore, I have been very emotional and craving things I would normally never eat. I took a test about ten days after my missed period and it came back negative but still haven't gotten my period. I don't want to waste more money by taking another test if I am not pregnant. Would just like some advise thank you!