My buddy got with the girl i'm seeing

Everyone involved is 20 years old, we're all at uni together.

I've been getting to know this girl, we've fucked maybe 15 times over a few months, I'm starting to like her a bit but it's not like i'm going to marry her or anything.

My bud has been flirting with her, and I was getting pretty jealous. A few nights ago he sent me snaps of her at his place claiming it was to 'let me know what she's like.' As if he was looking out for me or something.

I've since learned that he enjoys getting with 'taken' women and has done this to another guy I know.