I had a baby feb last year went on the depo straight away, but didnt have it from decemeber.. I thought i came on about 3 weeks ago but it turned out to be a tiny bleed and now i have sevear back pain , im so tired, my nipples hurt, and i feel sick every now and then, i did a test last week which came back negative? But had a slight very faint second line?? What could it be?