There are no hard answers here, L., and of course you can't give all the details I'd want to know before making a recommendation one way or the other. But here are the thoughts that jumped into my head as I read your post:
I am the oldest of 4 girls. I'm also shy, cautious about trying new things, and a born dreamer. My mom is very extroverted and hated my shyness, and always pushed me to be involved with people and become a pathfinder for my younger sibs. My most pervasive memories of my whole childhood, including my earliest recollections, are how miserable I was. My mom wanted me to be what I was not, and not only was that a horrible strain for me, it also left me with very little time to explore who I truly was. I had to do all that work, belatedly, as an adult, and at 60-something, I am still getting there.
One thing I have learned, through lots of independent reading about child development, is that free, independent play is absolutely essential to optimal physical and mental development. Kids "know" what they need, and those needs find their way into their games and explorations. Adults have for decades believed that we need to teach kids everything, but that is turning out not to be the case. Our desire to teach them certain physical and emotional skills is best if balanced by plenty of time for free play.
If you have your son enrolled in three classes (?) right now, it may be that he feels overloaded, in which case the strain could be showing in his behaviors. Might you consider cutting that back to one class for the time being, and see what changes occur in his overall attitude? He may, if given the opportunity, discover that he'd like more time in classes. I'm guessing that at age 4, he'd get more out of less structure.
I hope you find a balance that works well for your family. You sound like a caring mom!