HELP

Help I have a problem. I have lost my sweet, loving, little boy. He has been replaced with a little boy that I don't know. Don't get me wrong. he has his sweet moments but overall he has gone from sweet to monster in a couple days time. I don't know what to do!!!! He has been sick before and this has never happened. He throws fits and screams, he won't share, The other day he refused to get out of bed and come downstairs. He goes to bed mad and gets ups mad. He wont eat anything but junk and chocolate milk. You have to tiptoe around him and give him everything he wants to keep peace and I am not that kind of mom.( Sorry to say) He is so stubborn, you could spank( yes I said the word) him all day and he still wouldn't do what you wanted him to do. Before he got sick all I had to say was" Konnor I told you to pick up your cars" and he would say" sorry mommy sorry" and do it. I want my sweet boy back can anybody help me find him?PLEASE
Tomorrow is Sunday maybe we can all catch up on a little rest. Sounds good to me!!!!!!