Can anal sex cause nerve damage in the anus? i have less feeling of urge and have to strain to get the feeling after anal receptive anal sex?

The anus has a complex nerve/muscle system that functions like a purse string. It sends notifications to the brain about fill status and suggestion for emptying. Its natural design is damaged by repeated passage of oversized stools or by anal sex. The purse string mechanism can be overstretched leading to need for an anal plug/loss of sensation. That is an expected eventual outcome of anal sex.