Guys...(and girls) i need your advice on this one...?

A guy started working at the same company as me. We clearly had an attraction towards each other. Well, he took my number from the employee list and called. Even though he had a woman, we really hit it off. The face that he had a woman did not bother me. I am and was tired of being in ';relationships'; that produced anything more than a one night stand and thought this way, i would be ';safe'; so to speak. We discussed what we wanted from each other and we both agreed. We would have an open honest relationship and just be cool. Again, I was o.k. with all of this. We decided to keep things on the down low at work seeing as though rumors run through this place like crazy. I did however tell him that i did not care what he did outside of work but that I would appreciate it that he not ';mess with'; anyone else at work and if he wanted to then to just let me know. He was cool with that. Now, there is a girl in our office that since the first day has been following him around like a lost dog. It drives me crazy. I mentioned it to him and he blew if off. Told me that I was reading more into it than what was really there. I let it slide. Well, its continuing and it almost seems to be getting worse. So, I said something to him about it again. This time, he got mad and told me I was tripping and flipped the whole thing around on me. I know I wasnt right for even getting involved in a situation like this but is is o.k. for a guy to switch the game up in the middle and blame it on you? I knew that I could not call him when his woman was at home and I couldnt go to his house and I never did any of those things. His woman would pick him up from work and I just smiled and said hey. I respected him and our agreement. My question is do I have a right to be a little pissed off or am I, like he said, overreacting? My female friends side with me and my male friends side with him. Who is right?Guys...(and girls) i need your advice on this one...?
i'm with him tbh.. if you both agreed to have a casual relationship you don't really have a right to get hot under the collar because another girl is giving him attention.. you don't even know that anythings happened between them!! if i was him, i'd be a little pissed as a bit of fun has turned into a hassle..





anyway, as you say, it's not an ideal situation.. casual relationships never really work if the people see each other all the time.. in everyone else's eyes you're both fair game, but you clearly don't see it like that..