If he could before, he can again. I would use social stories about using the restroom, communicate with him that you’ll try again. Create a token system, everytime he is successful, he gets a star. When he earns 5 stars, he gets a treat. My son didn’t learn until he was 9.

my son was fully potty trained but seems like he doesnt wanna used the potty anymore

It is hard work....My daughter who is 12 just is now potty trained. It takes the school to help the most. Once they were on board taking and asking on a set schedule, we had success. She still uses a pull-up at night but has not needed it in over a year.

Yes Nehemiah go to the bathroom at school 3 time a day and ones at home after school

Does your son use the tolet at all? My son took, also severe, took almost two years to understand the whole poop in the toliet thing. I did alot of hand-over-hand, sitting him on the toliet every 30 mins or so, and made him help clean up. Hopethis gives you some help. :)