Could Spotting, Cramps And White Tissue Discharge While On Depo Suggest Miscarriage?

I'm on the depo provera shot and I started spotting about two days ago then today severe cramps woke me up out of my sleep. A few hours later lots of white bloody tissue came out of me. Now I have no cramps & little to no bleeding. I had unprotected sex two weeks after the injection and had unprotected sex again a week after that. Could this be a miscarriage?