What Causes Irregular Bleeding And Back Pain After A Depo Shot?

My names Paige I m 18 and about a month ago I got the depo shot and last week I started my period only spotting but with extreme pain in my stomach and back I stopped after 3 days , this morning I woke up and started again with an extreme amount of blood and clots and stil got back pain, I m scared and don t know what s happing , 2 years ago I was on the shot and had no periods at all but decide to get off of it but now I m back on it and things are going different and worse