Girlfriend

I will take anyone opinion on this , lately my relationship been really rocky and it fucking sucks sometimes but I try to work it out. My girl friend just started a new job about a month ago and when she started would not stop talking about this guy who looks so much like me. She told me she stares at him sometimes to eventually telling me she has a crush on him . Being honest to me I kinda accepted it as long as nothing happening. Then we were about to have sex and she starts bringing up 3some with me and other chicks at first to other people like her best friend or my brother and that kills the mood for me .Like 3 weeks ago she causally says I wanna bone any guy I see and would want me to have sex with her at work but never comes home horny for me. At this point I just think she wants to fuck other guys but still wants to be with me. Been together for 3 years and this is the longest relationship we had ever