naked lovebird jerking

hello my lovebird is approx 10 yrs old
his mate died 5 years ago and i threw the whole cage out and put him in a new one so he would forget...he did and has been fine since
for the last month ive noticed he has lost all his feathers around the front of his neck and he also has a small bald spot on his shoulder
it obviously bothers him because he acts like his neck is broke and keeps it tilted to one side, but he can move it to the other if i move his cage (he hates me so wont come close)

what could the problem be with him? he eats and drinks fine but once he was on his purch and continuously jerked his neck back and forth and wouldnt stop for the entire night

thank you so much