please help !!!

my cat hadley when grooming hisself or at any givin time rips out his fur with his teeth he is a male 12 yo and has been doing this for a few years his lower back is partialy bald i hate this and it really worries me he dosent have mites or anything like that vet checked him any one elses cat do this or know why he does it all help greatly appreciated

I am not any kind of expert. I'm sure someone who is will shed some insight soon. Since you said the vet checked him, maybe its stress related. Was there a big change for him when this behavior began?

I'm not trying to be mean, but your post was very difficult to read with no punctuation.

This is usually stress-related behavior. It could be that something stressed him out, possibly he was sick or something in the environment changed, and he just keeps doing it. Your vet can help you with a plan to make him less stressed.

Kitty tranquilizers can temporarily help reduce any stress. Also, it could be temperature related. When my step-mother developed a severe allergy to her cats, they had to move down to the basement (although they also could go outside). Stress from the changed environment, coupled with a new habit of sleeping on top of the furnace cabinet, prompted the older female to start pulling her hair out on her belly. But when the furnace was turned off during the summer, she would stop pulling it out and it would start to grow back in.