TMI Depo shot spotting

So I'm on my second round of depo. Everything was great after the first shot, until I got my period. I started bleeding kinda heavily for two months straight. I read that taking a large dose of ibuprofen a few times the day will control the bleeding, and it worked. But I found that I got pretty constipated and it wasn't a good solution, so I just dealt with it. When I went back for another shot, the nurse told it'll probably take a while for my body to adjust. So I got the second shot. At first it was good, but then when I got *active*, I noticed some blood. It normally becomes the most bothersome when I'm masturbating, tbh. The first time, the blood only appeared after I got my first period while on the birth control. This time, it appeared after a few weeks. It's a few drops of blood that show up right after sex. Some days it's not there, but that's a little rare. I'm taking the calcium and vitamin D that I'm recommended. Does anyone know what the heck the problem is? Or is this normal? It's really annoying.