Connection?

So at the moment I am sitting on my bed, my room mate, and her friends are around being their loud selves and my "friends" are off doing there thing. But I feel like I am becoming disconnected from them. During the week we hang out all of the time. And its great. I feel like they are truly my friends; but then during the weekend they go off to parties, that I am not invited to. And then when I confronted one of them today (saying that I did not want her to abandon me this weekend, shes going to a date party with a guy we barely know and who has a girlfriend too) she told me that I can't pressure her like that. And that I can always go to other parties. But WITH WHO??? My friends don't go to parties with me and I am forced to go to things with my room mate (Shes cool and fun but we have different friends, so I don't know any one at the parties). I don't really know what to do. If I try to make more friends then I feel like I am abandoning them, and I don't wanna do that to them....