Perhaps they don't think you're interested. Have you tried speaking up?
I don't think that it's weird to want to be part of something important, like a wedding party. You sound young, but I don't know anything about you. Perhaps you could practice on letting people get to know you by starting out with filling out your profile. Don't be specific, just what you're comfortable with.
You might look at how you interact or avoid others during family/friends get togethers. Could you possibly be giving off the impression that you don't enjoy what is going on or don't want to be involved any further? Or do you join in the conversation, focusing and listening to what others are talking about? Perhaps there are some mixed signals.
By the way....welcome, and nice to meet you.
