Relationship diaster

Have you ever experienced any problems in your relationship? I do! well, this might be a normal issue to anyone who's been in long term commitment with your partner. People do change over time, believe me! I've been through all the changes he had been and I have to admit that I myself changed too. From 2008 to 2011, we've been stick together really firm and nobody couldn't break us down unless we want to. Lately, I found out that he's making out with the new girl over his BB chat and I'm beside him lying on the bed. He doesn't mind me watching him chatting with girls but the thing is I DO MIND! I didn't noticed how far he's been reach to with that girl but I'm pretty sure that conversation was pretty smooth like the beginning of something. I kept watching him without saying anything until he turn off his phone to go for bed. He thought I'm okay with this matter, hell no! How am I suppose to be alright when my bf is chit chat with new girl and threw some flirty words, (lol..:P blah blah blah) Just think about it. I said it's time for bed and what he said to her was "we gonna continue discuss about this later".
What the holy fuck is happening beside me? He has more things to discuss with her when I am not around? When I brought about this matter to him , he simply said you don't need to worry just friends. HA HA HA! That's my reaction to his words. There's a rule in this world in case you don't know a bf and the girl can never be good friends without conflict with his gf. That's the nature, I hate it but it's true. No jealous or anything like that. Just pissed off the way he treated that girl is the way he did to me in the beginning of our relationship. I can't blame to the girl since I know guys are no good and always find a way to cheat girls. Call me pessimistic but I had really bad experience in cheating and breaking relationship in my family and also in the environment I've grown up. Talking about cheating remind me of my dad who left the family for his business partner wife. I swear by after that day I will never let my own family happen that.
I'm not looking for a perfect guy. Someone who I can learn on when I tired, who can swipe away my tears without asking why, who can stay with me for his entire life and the most important things is to love me and faithful to me. Am I demanding too much? I guess not. Anyway, I want to stay out of relationship sometimes. It's been really hard for me to maintain this relationship by one side while he doesn't care that much. Ending with someone can be a beginning with another one. Should I let him go? or hold on to him? Well, time will tell. All I can do is wait & see.