I went through this exact same thing with my son when he started preschool at 4.5 years. Almost exactly the same word were said. And his attitude was horrendous. I will add there is light at the end of the tunnel He is now 7.5 and it has stopped ( yes it went on this long) it eased then got worse then eased again and slowly went away.

My nephew has just started the same behaviour over the last 6 months and he was in preschool this past year as well.

Good luck. The only thing that worked for us was to try and ignore it all. The more attention we paid to his crying and tantrums the more he did it, once we stopped they slowly stopped as well. He still has bad days as he has a bully at school unfortunatly but over the past 3 months he became friends with this child and school became fun again which in turn made home life more fun...