Is there a way to politely ask someone to leave you alone for the moment? They are literally in my house inside my room.

Look at your phone and say "I really have to take this".....

Ask him to go downstairs, please, please, and get you a glass of water.

Quickly while he is gone, make a large sign that says "Do Not Disturb! Quiet Time Needed!" Tape it to your door and close the door.

universal habits are still habits

Tell them you think you are gonna barf. No body wants to be around that.

Why, yes there is! A hefty swipe from a knotted rope!

With some you may have to literally go into the bathroom and shut the door.