I have a red spot on my lip that only appears after a meal, when i am extremely anxious, or when i am sexually aroused. what could that be?

Sounds like a: Vascular(related to blood vessels) lesion on your lip, based on what you describe. As during periods of arousal or anxiety, there are changes in blood flow that may make your lip lesion more prominent. I would strongly encourage you to see a dermatologist about it, so that it can be better characterized.

Probably vascular: This sounds like a small vascular lesion. Get it checked out by your primary care provider/or Dentist.

Here are some ...: Your constantly recurrent sole spot on the lip seem related with whatever the conditions may incite some increased circulation to that spot. Histologically, i.e., under microscopy, that spot may consists of more capillaries like a hemangioma. And this spot should carry no clinical concern as long as being not bothersome in any way so leave it alone and save time and energy to worry about others...

Vascular : It sounds vascular since you see it at times when vascular dilatation could be expected. You need someone professional to see it to know for sure. Hope this helps.