Hello! how did the autism evaluation go? My son has sensory integration disorder and tactile issues are definitely prevalent with that diagnosis. On the other hand, my sons, two of them, one neurotypical and one neurodiverse, have resisted things at different periods of time like getting out of pajamas on some days, wearing same clothes for a few days in a row and not wanting to shower. I think it is a universal boy thing to go through a period of mom thinking they need to do these things (throw brushing teeth and hair in there too) but they just don't wanna. The one thing that I do with my ND kiddo is to make sure I have extra of what he loves clothing wise. He loves a certain kind of pants--- I get a few pairs. Offer those when it is time to change clothes. Also, figure out motivation or what motivates them. (for my second son who is neurotypical, it was when he noticed girls. lol, he got real serious about hygiene and clothing at that time).
It sound part of the whole to me. It's hard to know how to discipline a child who is acting out of some problem with brain function. Does he respect you on other things you try to teach him?