I'm worried my boyfriend has a crush on my best friend?

So for background; I've been dating my boyfriend for a year and a half and we have a very good relationship. He's affectionate and loyal and just an overall great guy, I know he wouldn't cheat. & I have been best friends with this girl for almost a year now (We're all 18). My boyfriend didn't like her at first but once he got to know her, he told me that she was the favorite of my friends. Things were good and the 3 of us always hung out in groups (the 3 of us have the same friend group) throughout the year and stuff but for the past few months, I've noticed some things that just seemed very odd to me. Now before I say this, I will admit that I am a very insecure person who tends to get jealous easily but some signs that I've noticed have just been a little too bizarre that's it really hard for me to overlook. For starters, whenever she's over, I noticed that he suddenly becomes very smiley and talks to her for most of the time. I've also noticed that whenever we hang out in groups with many people, I've caught him staring at her for long periods of time. Not only that, but he is someone who NEVER wears cologne but recently over thanksgiving break, my best friend visited from college and I noticed that one of the days the 3 of us hung out, he was wearing cologne for some reason. He also always takes her side when I tell him about our arguments, and always asks stuff about her. I don't know if I'm overreacting but I really hate being insecure about something like this.