I have cellulitus in one butt check it's pretty big will I need surgery to remove dead tissue?

I am sorry you are having this problem. As you know, it can be =come very serious. Follow your surgeon's recommendations closely. If it is still getting worse despite the oral antibiotics, the next step is likely admission to a hospital for IV antibiotics and possibly a surgical debridement. 

Hello dear!!
Thanks for the question and provided information as well.
Unfortunately, without pictures, it is very difficult to give you a proper answer.
l recommend you to make an appointment with a board certified plastic surgeon to talk about your goals and anything you need to know.
Good luck :)