Change all your Facebook, Myspace, and other social network friends to those who sky dive, so you don't have to look at any more wedding photos.
Originally, your posts were more about your boyfriend and how he was always able to make friends with people to the point of being asked to be in weddings. Now, you have changed the focus of your resentment to brides.
It sounds like you want to be seen as an extension of your boyfriend without having any of the attributes he has.
Groom: Let's invite X to be an usher. He's been my friend for 3 years.
Bride: His gf looks nice too. I'll ask her to be my maid of honor.
It just doesn't work that way. Places in weddings, especially on the bride's side are generally reserved for long standing friends, relatives, children of relatives or friends, but rarely girlfriend's of a groomsmen or usher (unless they also belong in one of the other categories). That's just the nature of weddings.
You've admitted you don't make friends easily. You've done a few social obligations, hoping to get in a potential bride's good side, etc. That just doesn't work on the bride's side like it does on the groom's side.
The old addage insanity is doing the same thing and expecting different results.
You can't cultivate the type of relationship most women base their choice of wedding participants in a few short months.
It can be different with guys. They usually have a best friend or relative they'll ask to be a Best Man. Then, groom's men and usher can range from frat brothers, relatives of the bride, to a guy he met two months ago. It's just different.