Have a canker sore on lip (>week). excruciating. barely sleep, close mouth, eat. only been able to eat ~1,000 calories in past 4 days, starving. help?

Be sure of diagnosis: Get examined especially if that bothersome. Canker sores are common aphthous ulcers of mouth that occur situationally often in response to stressors, are bacterial or viral, & can be treated topically with many OTC products that reduce local discomfort &potentially speed healing. However, oral/dental problems & a number of systemic diseases cause canker sore-like lesions--Crohn's, Behcet's, STD's.

Get seen: A simple fever blister hurts but not this badly. You may have another infection too, Go to an Urgent Care center today.

See Dr.: Sounds like more than just a canker sore issue. Get to the Dr. and be evaluated.

Maybe viral: See your doctor for evaluation for possible viral cause. You may need antiviral medication.