18mm long philtrum that keeps me from smiling wide because I get a line on my philtrum. (Photos)

Good day! Thank you for providing photos with your query. I believe you are a good candidate for a lip lift so ask your doctor about lip shortening which has small incisions placed at the base of the nose under the nostrils. This shortens the distance between the nose and the upper lip and will also allow the lip to “roll out”, creating a more "pouty" look.This procedure also drastically improves the aesthetic of one’s smile and facial proportions. It is tailored for each patient to create youthful, natural looking results that can create a more proportional smile and reduce the signs of aging around the mouth. 
Find a board-certified plastic surgeon that has extensive experience with your case and discuss realistic goals and expectations. Best of luck! #RealSelf100

A subnasal lip lift would be appropriate to reduce your philtral distance from 18mm to 13mms. The only difference in subasnal lip lifts is where the exact incision is located along the underside of the nose.