I'm a very healthy person but don't eat fruits/veggies every day & never have. I'm concerned about oral cancer risks.

Night great. Oral cancer which frequently appears as leukoplakia first has little to do with the nature of the diet and as to how much fruit and veggies are ingested. Most have a serious history of alcoholism and smoking. As this group slowly diminishes, those with exposure to HPV come into play in the induction of squamous Ca.of the oral cavity.
Smoking,drinking. Highest risk of oral cancer from heavy smoking, drinking. You're young enough to benefit from a chance in diet.