I need some good love songs that make you sad?

Ok so Ima a guy who's having some love problems because I... guess you could say I've falling in love with my best friend but she's totally obssesed with some other guy (who has a girlfriend) so I've just given up and am gonna try to get over her. But I need some songs to listen too. I guess you could say those love sad songs that make you cry even though I don't really cry. I have a lot so please try to name as many as possible. I'm not into rock but I'll try it if its good. I want mostly slow songs. Bruno mars, adele, leona lewis, jason mraz type songs. Thanks