I have a bitter taste in the back of my mouth now for a week with no other symptoms. i've had no change in lifestyle/diet. how do i get rid of it?

Go see your doc: Bitter taste in the mouth may be a sign of Reflex Esophagitis. You could try an OTC med call Prilosec and see if your taste returns to normal. I would see your doctor as he/she needs to exam you and may need to order tests (H.Pylori, Possible ENT consult, or GI consult; Upper GI series.....) He may also culture your throat as well.

Get it checked: Several possibilities, including periodontal disease, tonsilar issues, or reflux from the gut. A dentist can check for periodontal disease. An ENT can check your tonilar areas.