I was hoping to have a hair transplant however, I've been losing a lot of hair from the donor area (i.e. from the sides and back of my lower scalp), even more than the areas on the top. Is there any procedure to regrow all my lost hair? How successful would hair transplant surgery be?
Hair transplant surgery wouldn’t be a viable option for you at this time since you are losing "safe" hair and the reason for it is undetermined. Harvesting hair from areas vulnerable to loss significantly increases the risks of permanent transplanted hair loss later down the road.
Since genetics typically only target hair on the top of the scalp, the first thing you need to do is find out why you are losing hair from the sides and back of your head. In my opinion, consult a dermatologist for a full medical evaluation and scalp analysis to help narrow down the cause of your hair loss. Treating the areas will depend upon the reason you’re experiencing balding in these areas.
I hope this helps.