We're both college students and have been together for six months. He says he's in love with me, but there's this girl he dated a couple years ago (he dumped her for another girl - not me) and whenever she's around I sometimes catch him taking prolonged looks at her and deliberately trying to make eye contact with her. He was in touch with her only a week before he asked me out, and I don't know what exactly went down between them, but I know he's not in contact with her anymore. Is it possible she's just his "go-to" for sex when he's single? But why would he be looking at her so much?