Something fishy and I can't put my finger on it

I never realized that I would feel so wounded thinking about my son's shortcomings.  All my life I have copped with my own insecurities by finding a unique niche.  I know I'm not the smartest or the coolest or the sweetest.  But I can be sparkley when others are shinny.  Like in college.  I know I am an awful essay writer, but my American Literature professor said that I wrote from the most unique perspective of anyone else in the class.  I guess it is a survival instinct.  
For the last three weeks I have been teaching a half day preschool class on Monday mornings.  I signed up for this because I wanted an opportunity to participate in LM's education.  I feel like I miss out on his life and development while I am at work.  I did not realize how tough it would be for me to see him in contrast to the other children.  He can be so withdrawn and reluctant to participate to the point of defiance.  He lacks the awareness and eloquence of the other kids.  Daycare has told me a couple times that he did not want to do circle time, or tutoring, and I used to dismiss these things as not stimulating enough for him, but now I am starting to get worried.  I am remembering that there used to be a time when he would sit down with me and draw or paint or play with Play-Dough.  But, now all he wants to do is play with trains, or cars, or jump off of things.  His comfort zone is narrowing.  Although his social regression is not evident at home, I see it now at daycare, birthday parties, preschool and the gym: he doesn't play with other kids anymore.  This Sunday I missed my weekly yoga class (my 'Reset' button for the week) because he did not want to go into the gym's Kid Zone.  It is a jungle gym play ground!  What kid would not want to go there!  He wanted to sit with me instead.  I just know that something must be going on with his little brain.  Something that he can't explain or does not feel comfortable talking about.
I am realizing that he is not progressing the way that he should be.  He used to learn things very quickly when he started daycare, and he was interested in one-on-one time.  But, now he runs away from anything that resembles instruction.  Like, we got these balsa wood airplanes and he was so excited about flying them.  I was trying to teach him how to wind the propeller: take one finger, like the number one, and spin it around the propeller.  Well, learning that was too much work and he just went to play with something else.  Then, I have been thinking about how he has been trying to learn to count for almost a year now, and he still says, "one, three, four, five." 
I was thinking that this was all just part of his personality and I shouldn't pressure him to learn at such a young age. That all kids are different and I should not compare.  But, now I really feel like he is having issues and I'm worried about him.  
I just wish that I could hug him and make it all better but that's not working.