I Don't Know What To Do

So I'm a teen who is in JROTC and am about to be promoted to XO(which is a very good but busy position), and my "boss" is a guy that I've known for a while. Well we became friends and he and I talk and mutually bash each other like friends do. But sometimes he snaps and starts spouting all these hurtful things about my family, education, and body and it really hurts me. I usually just brush it off because I'm not the type to make it a big deal. He also talks about h and his gf's relationship to me. Like INTIMATE details and I'm like nah honey I'm good ain't nobody want to know that crap. But ANYWAYS, recently I've noticed he has started to kinda stalk me? Idk if that's the right wording but he's pretty much around me all the time and he just broke up with his girlfriend too. I know his friends and they say that he talks about me in sexual ways to them and I feel so uncomfortable around him now. I feel like I should tell someone about how uncomfortable he's making me when he talks to me like that but I know if I tell someone either I will lose my position or everyone will hate me because he is pretty popular too...I don't know what to do