Before others saw the pizza, there was free pizza in the break room so I took the whole pizza
You really kept an entire pizza for yourself?
I was too proud to share my good find with others.
I do not think that taking the whole pizza was okay. You should have left some for your coworkers to enjoy.
I don't care what my coworkers think, I deserve it and I didn't want it to be wasted!
I don't think the pizza would have been wasted, and in fact, if you told your coworkers about it you could have all eaten some of it. I think you should apologize and buy them a new pizza for lunch.