<human>: My boyfriend acts differently with his friends when I'm not around.  He is more flirtatious with girls, less reserved in general. (I can't really say any specific situations because he too is a redditor :/) I had a feeling about this from overhearing things and I was surprised that I hadn't known about them from him... 

When confronted, he admitted to acting differently and says he didn't think these things were a big deal and he doesn't want to embarrass me by being overly obnoxious.  It makes me question if he really wants to be in a relationship with me or if he is just scared of being without me and that's why he has "good" behavior.  It also makes me wonder if I really know who he is b/c he acts differently when I'm not around.

How do I get him to just be himself, all the time? Do I really even know who he is?  I love him, but at the same time I want him to be happy... and maybe I'm being insecure but I'm not sure that he's really ready for a serious relationship and I am concerned that he might need some time to be single, grow up, and figure out who he is and what he wants.  Are these feelings I'm having absolutely insane!?

Any thoughts?

23F, 22M
Dating for ~3.5 years

Can you succinctly summarize the text in 1-3 sentences?
<bot>: I recently found out BF acts differently (less reserved) with his friends when I'm not around. Is it possible that I don't know who he is after 3+ years?