Hello, My Name Is Chelsea. Well I Have A Question

Hello, my name is Chelsea. Well I have a question maybe you can help me. About 3 months ago got on depo. But before I did I didn't have my period for about 2 months. I took pregnancy test back then. Well since my depo is out of my body some odd reason I am just spotting without no pain. There is days i get pain. But today I didn't. I i've been to the doctors about having weird pains when I was on depo and i even told them about me missing my period for 2 months before I got on it. It seems like no one can figure it out what it is. Now I am spotting why?