I discharged a large m of tissue it wasn't a clot... what could it be?

I've been bleeding for about 2 months straight after I had the Depo shot. And last night I discharged 2 mes of tissue. The first was abut 1" by 1" and was dark red in color and almost looked like liver tissue. The second was about 3" by 1" and it was lighter in some areas and darker in others. I'm positive it wasnt a clot. I was able to wipe the blood off and I'm pretty sure I could see vessels in it. I haven't bled any since and I'm just wondering what it could be and whether I should call my doctor. In the past 2 years I've had 2 LEEP procedures to remove precancerous cells from my cervix. I went 3 months ago to have another pap and it came back clear. Thanks for any help!