Sexual harassment ?

So here’s some background information first.. so I’m in jrotc and for y’all who don’t know Jrotc is a military run program in highschool that is made to install patriotism, self confidence, leadership, discipline and respect. I’m a junior and an officer in the program. I have a vehicle so I give rides to fellow cadets if they need them so there’s this one officer who have been asking me for rides and Every single time I give him a ride he makes these extremely offensive and sexual remarks toward me, mind you I’m not single I’ve been with my boyfriend for 3 years now. I don’t know how to approach the situation I don’t know how to politely tell him I don’t wanna give him rides anymore and I feel like I should report him but I’m scared if I report him for harassment then he’ll tell our instructor that i vape in my truck (which is illegal cause I’m 16). What do I do ? I don’t feel comfortable but I don’t wanna potentiality lose my officer position I’ve worked hard for 3 years to get, should I just deal with it ?help me out please.