<human>: Can you give me a shortened version of the text?

My girlfriend had a birthday recently, and to celebrate we got together with a small group of friends.Unfortunately, this situation left me feeling awkward and like something of an outsider. See, we were all friends through the first year or so of college, but then most of them went on to become RAs on campus and, suddenly becoming busy with RA duties and other things, I found myself left behind and feeling somewhat abandoned. I dealt with it at the time and moved on with life, but, as something similar had happened in my senior year of high school, it stung a bit. Now anytime that I get together with them as a group I feel like an outsider, and like there's an elephant in the room, a feeling made all the more real by the fact that they often seem to think that I was with them in some of their situations, or had an experience that was more like theirs. It just sort of leaves me standing there thinking "yeaaah, about that" My girlfriend and I have a pretty communicative relationship, and I feel like I should tell her. Just looking for input. What do you folks advise?
<bot>: Feel like an outsider around friends that I used to hang out with more, looking for advice on telling girlfriend (who is a part of that group).