Um why all the run around? Why not just say that you don't want him to stay because you need time to yourself for those days and you are sorry but maybe can make up for it to him some how in the future. If he is truly a friend, he will understand, but if he bitches and complains or moans about it and never talks to you again then what's the big deal? Sounds like you wouldn't mind that happening anyways.
This is what I hate about people. Friends can never tell friends the honest truth, they always have to lie to each other, yet enemies can always tell you what they think of you. The really good friends are your enemies because they will never lie to you.
Don't lie about it, that way you don't look like an idiot when you get caught. Just be honest and tell him straight up that you need this time for yourself and you are sorry you can accommodate him for that time.
Problem solved, no need for more lies and you can at least have some peace of mind that you didn't have to manipulate the situation.
Have some balls... face the truth...