I don't know whether this is similar, but my son had a similarly terrible time with his first preschool (a perfectly fine school, by the way) and still remembers how sad and lonely he was there, and how bored. Our solution was to put him in a wonderful, stimulating and not-very-structured co-op preschool. It took 2-3 months for him to separate from me, which meant I was going to preschool that whole time, but it was a lovely, nurturing place that he grew to love. Just a thought. Good luck!