Could I be pregnant ? PLEASE HELP

I'm 8 days late for my period. I just got on depo Provera 7 days ago. When I had sex with my boyfriend around 5 days ago I started bleeding as If I'd started my period but after that I never bled anymore . My period never came & the doctor said it takes a week for the birth control to kick in and maybe a couple months to change your menstrual cycle. Took an at home test but came out negative . SOMEONE PLEASE HELP, I have no one to ask..