Perhaps too attatched?

I have been friends with my best friend for almost 2 years now. I have become extremely attatched to him. He is gay, and I love him to death. He has done a lot of things for me and with me and he has made me a better person because that is who he is. We have been living together for 9 months now. Here is the problem, I hate when he meets new guys. It is not that I want to be them or that I want him that way, it is pure platonic love I have for him. It just makes me upset. Now, for some background information, my biological father ped away 3 months before I was born, and my mother got re-married when I was 6 to a complete ****** who constantly put me down my whole life. I have a step-brother too, who is an alcoholic. So, my feelings towards guys are not that great to begin with. Could it be that he has filled an empty void in my life and whenever he meets someone, I feel replaced? I just don't know what to do. I hate feeling this way, and I should want him to be happy. Suggestions?