Can A Hyper Vascular Area In The Uterus Cause Headaches And Nausea?

I had a miscarriage 5 weeks ago. At that time the OBGYN thought that based on the ultrasound I would be able to complete the miscarriage naturally. About a week after the miscarriage I started to experience headaches. The headaches vary in intensity everyday. I've also been feeling very dizzy and in the past week I've also developed nausea. I went to the ER today looking for answers for the headaches. All of my blood work came back good. Five days ago my beta hcg was 7, and today it was at 3. The doctor was concerned why I still had hcg in my blood after 5 weeks so he did an ultrasound. They found a very small "hypervascular area" in my uterus. The ER doctor thinks that it is retained products and wants me to have a d&c. At the beginning of this week I got what I thought was my period, so my question is could the hypervascular area they're seeing be from a period, or would that appear different? Could the headaches/nausea be from retained products?