I used a quote in a homeschooling article: "Education is not the filling of a bucket, but the lighting of a fire." Yes, you can send your son to preschool and beyond. He can be made to memorize lots of facts and figures. But is this true education? Has he learned to love learning?
Read How Children Learn or anything else by John Holt. Visit our homeschool page and read some of the articles there. Relax! You've done a great job with your son up to now. Let him be a kid, exploring, building, and having fun. In a short time, you and he will discover what he's good at, and what he loves to do. And when that happens, you won't be able to hold him back! That is true learning.