What is it with men nowadays, why do they think there so wonderful?

sorry I need a rant, but men really really wind me up! I am so glad I have two girls. I suppose this stems from todays antics on facebook! This fella who I sort of know, he was my older brothers mate. added me proper started flirting, sending messages saying im beautiful, la la la... knowing i'm heavily pregnant. so I asked him, why such a nice person like him was single, and he tells me he is seeing someone, but isn't "feeling it" and told me he got chatted up by so many "hot" women. but he didn't flirt back, cos he was a good boy! but he can start talking to me and calling me sexy gorgeous whatever and thinks this is okay!!! what is the problem with men nowadays, always keeping girls there not really interested in hanging on, while they keep there options open for the next one. and being blantently honest about to the next woman. and thinking its ok. and they think your come running to them and think there so amazing. why do they think i am desperate or something I hate men!!!!!