Depo shot bleeding

I started the depo shot birth control exactly a year ago. I have had 4 injections and am due for my fifth. I am very very concerned though, out of the last 12 months since I started the shot I have spent 10 of those months bleeding consistently everyday. I have about two weeks of no bleeding after the shot, then I bleed until the next one. This is not just spotting bleeding either. I have to replace a regular tampon every 4 hours or so. I’ve asked my doctor for answers and she swears it’s normal and “just part of the process”. But I feel like bleeding that much for that long cannot be normal. Since starting the birth control I have developed anemia and the mood swings are absolutely awful. Has anyone had this issue, is my doctor being truthful with me and I need to just stick with it or what. Any help is very much appreciated!!