Did I have a miscarriage?

I'm on the depo shot but the last 2 weeks I've been spottin and I had very bad cramps 2 days in a row!! Now the bleedin has stopped but I keep gettin "chunks" of blood like a blood clot! I jus had a baby 4 months ago! And I haven't took a pregnancy test but idk if I'm pregnant or not do u think I had a miscarriage or jus a side effect of the depo?