Choose the correct options

A: I've got a terrible toothache. [Can't|Could|Should|May]you bring me some painkillers?

B: Sure. [Shall|Must|Have to|Must]I bring you a glass of water?

A: No, thank you.

B: You [should have visited |should visit|must have visited|must visit]the doctor last month!

A: Oh, I forgot. I [must be|should have been|can't be|must have been ]busy with my work. It hurts so much! If nothing changes, I [will not be able to |can't|couldn't|am not able to]go to the conference tomorrow then.