What Causes Uterus Lining To Be Bumpy?

I am 33 years old and had a miscarriage at 8 weeks in March. I had a D&C and have had two menstrual cycles since. However, in between the periods I continually have brown discharge/spotting. I saw my doctor last night and he said that I may need to wait another month because the lining of my uterus appears "bumpy". I assume this is what is causing the brown spotting. Any insight as to why this is happening is appreciated and any recommendation as to whether to wait to try to get preganant again because of this? Thanks.