Questions: Relationships

Hello I'm 20 years old and in college majoring in business administration. I have a friend in college who is 23 years old and he's a veteran from the air Force. He recently told me that me and my girlfriend are not going to last and we're going to break up eventually. My friend told me that when he was younger, he was made fun of by girls back in school (including high school for being overweight). before the military, he tried to get with women, but he got rejected a lot by women. He's now fit and now he's trying to take advantage over it. He said that he's trying to hookup with most girls as possible. He only goes for girls who looks for relationships to use them and to make the girl feel bad once he's done with him (because the girl was looking for a relationship; not a hookup). He said it's not fair how back then when he was younger everyone else was getting in relationships while he was single. I keep telling him what he is doing is wrong, but he won't listen to me.