Miscarriage?

So I got the depo shot July 30th, my period ended August 1st. I was 14 days late for my period in September, I figured it was the shot. I started spotting & I've been bleeding for almost two weeks and its gotten heavier. Today I noticed something odd on my pad & I don't know what is it. Could I have been pregnant and miscarried? I have a doctors appointment tomorrow but can someone give me an opinion?