Well, it can take a women anywhere from 3 months (if it's her first injection) to 48 months to get pregnant on depo/after depo (the 3 months is while on it, of course) as usual, it depneds on the woman but studies find that overweight women take longer to get pregnant after depo that fitter women do. However, I don't think it should interfere with a pregnancy test whatsoever.

I dont know cause see pee test kept on coming bk negative when I did a blood test it came back postive and im 4 months pregnant... That why I was asking

Yeah, I don't think it is from birth control. It may have something to do with it, but I doubt it. My friend was four months pregnant when she found out she was pregnant too. She had taken five home pregnancy tests, seven pee tests at family planning and two blood tests that all came back negative. She even had a pelvic exam and they told her that she wasn't. But, low and behold she was pregnant the whole entire time. The third blood test finally came back positive.
Silly situations.