D & C Question for those who understand?

I know what a D & C is. I had one 12 years ago after a miscarriage. I Guess im confused bc today after seeing my OBgyn, i was told i needed one. I am not pregnant. I had a healthy baby boy 7 months ago today. The problem is, at my first check up after delivering, i was given a depo shot and only one bc my husband had the vasectomy. So basically i have been bleeding non stop for 7 months and now i need this procedure and blood work done to see if the reason im weak and tired is the bleeding. any one go through this? Thanks for taking the time to read this.