Could my son be autistic?

Sounds autistic to me, I am actually autistic myself (Aspergers Syndrome) and I too find myself to focus on the most weirdest things without realizing it while simultaneously flapping my hands or squeezing my hands against my cheeks and moving my fingers. Autistics are naturally socially awkward which explains your sons lack of social interest (I can be socially awkward too). Autistics also have trouble expressing themselves which may be the explanation for his pain tolerance but that could be just part of his personality. Try giving your son some art supplies or something to do with music and see what he does, autistics are known to be naturally interested and gifted in art and music. My advice for you though is to not treat hi like he is autistic and treat him normally, that's how my family treats me and because of it I think of myself as normal and fit right in with everyone else, a lot of people i know didn't even know i was autistic until i told them or they asked about my hand flapping, none of them treat me any differently than they did before they knew I was autistic. Don't be embarrassed or disappointed about it some of the greatest people in the world were autistic such as Albert Einstein or Thomas Edison who both had Aspergers Syndrome