My boyfriend and I have been together for three years, I am 20 and he is 23, he is my best friend, we have a fantastic sex life and I have always trusted him. But the past few months he has been giving his number out and flirting with his ex as well as girls that I know on the internet. When his ex asked him to go to the club with her he said "you should just come over tonight and dance for me instead". He also tells other women we know how sexy/beautiful,etc. they are and our computer internet history is full of his exes pictures. When I talk to him about it he tries to justify it but ends up just talking in circles. This is killing me, should I be worried?