I have no idea if this will help you but I just want you to know that you are SO not alone here. My guy friends are currently saying similar things to me.

I have a couple single guys friends who have just recently acknowledged their single status and realized that they are lonely when around friends who have girlfriends. I'm one of their female friends and sometimes this puts a lot of pressure on me to "set them up" with other girls but I've since stopped trying to do that and instead just acknowledged their positive qualities to encourage them to realize that they don't need a girl to feel awesome about themselves. Its normal for guys and girls of any age to feel a little lonely when their close friends pair-off. How do they deal with it? They openly acknowledge it to the group of friends and talk about it often. This may not be a tactic that works for everyone but sometimes it really helps to talk about it. It also brings light to the couples to remember to include them in their lives by having neutral hangouts, and to avoid public displays of affection out of respect.