Choose the correct word i must/ should have been mad to

Choose the correct word
i must/ should have been mad to enter the karaoke competition last night. What was i thinking amp; I really cant/should have thought about it a bit more carefully. Why did i agree to it when i could/would have stayes at home and watched a DVD instead? But no ! I мейд a compete fool of yself in front of all my friends. It might be/have been all right if they'd given me a song i knew. Bit it was this really wierd song i'd never heard before. I cant/mustnt have got any of the notes right. It was so embarrassing