Am i just jealous?

I've always been the kind of girl whose group of friends consists of mostly guys. I do have my close girlfriends, but considering I grew up with just my dad and brothers, I tend to find myself relating to guys moreso than girls. Thus far in my life, it hasn't proven to be an issue. My guy friends and I have always been very "friends only" and it seems that every party is ok with that. Until now.

See, one of my really good friends, we'll call him G, has a habit of "hooking up" with some of my girl friends, and it rarely ends well. It generally ends with them hating each other, but I've always been ok with both of them, so it's never been an real issue for me. Until now. See, G recently went to Italy to study abroad, and just before he left he started hanging out with my friend J. Since then, he's asked me how I would feel about them being together when he gets back. I've made it pretty clear to him that I would definitely not like it, because J is a very sweet and rather innocent girl, and I don't think G would be good for her. Now while I haven't come out and specifically said that, I think he at least kind of understands where I'm coming from.

At least I thought so. Until J texts me "just to let me know" that they've been videochatting while he's been gone, and they both really like each other. Now I thought I handled it pretty well, but I guess not because apparently J went to G and told him I was mad that he had skyped her and not me.

While I don't think that's entirely true (I mean, I don't even HAVE skype) it got me thinking. Maybe things have changed, and I'm not ok with just being friends with him anymore. I can't decide if my opposition to their relationship is really for my friends good, or if it's just for my benefit.

And I know you Xangans can't tell me how I feel, but what I want to know from you is this. Assuming I do like him, do I let him know that's why I'm not ok with this new found relationship? Or is it not fair to my friend for me to bring this up now, when they might just be starting something? And assuming I don't like him, how do I let him know that it really is just the relationship and the outcome of it that I'm worried about, and I'm not just being a crazy jealous B****?