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

I have a pretty happy relationship with my current boyfriend except for one area:  his seemingly obsessive attitude towards his best friend's gf.  He would talk about:
-what books he wants to buy her when we're in a bookstore
-compare our cooking abilities
-her breasts
-her sex life with his best friend
-when we argue about his relationship with her (they're overly flirtatious with each other), he would defend her and say that they're just close friends.

I don't know if these are red flags or I'm just a crazy jealous girlfriend like he claims I am.  Please help me Reddit!
<bot>: Boyfriend obsesses over his best friend's girlfriend, claims I'm just jealous.  I'm not sure if I am or my intuitions are correct.