What wrong with me?😭

Ok so my ex and I are friends and we tell each other if we like this person or that person. So anyway there's this girl in my homeroom, she acts super innocent and she's really popular. I was talking to him yesterday and he said he liked her and he said " didn't you see me starring at her in the line , I was looking at all of the details on her face and I love them" and I'm like trying not to cry because he was behind me in lunch and she was in front of me and he kept smiling I thought he was smiling at me. I wanted to tell him to stop smiling, but comes to find out he wasn't! I'm super sad why?