<human>: Summarize the given text in a few sentences.

This is my first time posting here for advice, so I'm sorry if I make any mistakes. 

I've (20F) been dating my boyfriend (21M) for a little over a year. He's very good to me, and we connect very well emotionally. We do not live together. He's my best friend, and I don't think he'd ever cheat on me. However, this is my first serious relationship, and I guess I'm a bit insecure. I was a virgin when I met him, but he's had many girlfriends before me. I don't have much experience with men, so I was just curious as to whether this was normal or not –

I heard along the grapevine (from mutual friends) that my boyfriend would act really flirty with this girl in his class throughout our relationship. She's not in his close-friend circle, so I never got a chance to meet her, but I hear that my boyfriend thinks she is very beautiful. On numerous occasions, he would talk about how "hot" she was, and how he enjoyed how "flirty" she was towards him. He would (jokingly, hopefully) lament the fact that she had a boyfriend. This was all heard along the grapevine, of course. 

I know my boyfriend loves me, and would never cheat on me… However, if this girl were to suddenly be single and available, and if she were to throw herself at my boyfriend, my biggest fear is that he would accept her with open arms. 

Is it normal for guys in relationships to obsess about other girls?
<bot>: – insecure dating n00b wonders if other guys in relationships openly talk about flirting with other girls and wanting to have sex with them with friends.