Third Wheel Syndrome

I lately have been feeling like a third wheel to most of my friends here in the city. Most of my friends are people i've only met since May and they in turn have their own friends and now most have boyfriends or fiances. They of course invite me along with no qualms, but it doesn't help me from feeling like I am just along for the ride because they feel sorry for me. I know that this isn't the case, and more than likely just my imagination, and may be an attack from the devil, so i'll keep on pressing on!