He isn't around many kids his age, so I'd be surprised if he's trying to "fit in" at this point. I expect that when he starts school in August. But maybe he is picking up on his difference at the playground.
It doesn't take much, we adults are so used to 'tuning out things' - one lady in a grocery store saying 'My My - well look who is reading!' in a snotty tone can be enough for these tender things.
In general I think 'flexibility training' is very important for these kids who seem born with an internal intuition that is hard to overcome.
Start with telling a few stories from your childhood, and your recent about how you first saw a thing one way, and then another.
Show a few 'Vase or Face' pictures, and the one with the fork in the coffee cup, to show how our brains are 'making stories' all the time, even when we don't have all the information.
Then praise praise praise anyone, including your child, who shows the slightest bit of flexibility in their thinking. Lather-Rinse-Repeat for about 10 years....it takes a while.
Love and More Love,
Grinity