Please Help.. Pregnancy after Depo

I'm 22 years old. I had one cycle of depo(3 months) Started in October ended in December. Had some spotting in January then it just stopped. I still have no AF but I've felt a few cramps and I've been nauseous the past two mornings and I've also been sleeping a lot more lately. I took at test an hour ago but got a BFN. I'm so frustrated does anyone have any advice for coming off depo and getting pregnant ?