I think I am preg. On depo shot, could this effect my baby?

Okay so I just had my baby girl 6 months ago. I had the depo shot before leaving the hospital. I have felt a hard lump in my stomac area for awhile now and it seems to be getting bigger. If I lay on my back and have my hand on my stomac I can feel something doing flips and twisting. They did not give me a pregnancy test before giving me my next TWO shots.. Please help and do research. Can this hurt my baby if I am prego? I know there is a big possibility I will miscarry but what if I don't, will this cause down syndrome or anything else? I am really worried please help.