I don't get invited anywhere why?

So id first like to say I'm 19 year old male.. I'm not a loser or weird or annoying.. This is exactly why I find this so troubling.. During high school I always had many many friends and would go out endlessly but now that I'm older I've grown out of the texting facebook ordeal and I feel more mature than most people my age.. Don't get me wrong I love a good party and all that accompanies it.. I a, usually the life of the party, I'm great at making people laugh and I sincerely get along with everyone I meet and no I'm not just saying this.. However, recently I've been noticing that I don't get invited out places such as today and it really gets to me. I've been in a relationship for the past year and a half do you think that might be one of the reasons? Like I said I'm not very digitally social at all anymore as I see it to be a waste of time, could this also be a reason why no one invites me places? The last party I was invited to was over a month ago and it's finally getting to me. It really makes me sad because like I said I usually am very extremely outgoing. I attend ASU and I find it a little difficult to make friendships because the people in my classes aren't very talkative at all especially since I'm majoring in political science and my other classes are philosophy lectures so people tend to be more about books and studying. I feel like I need real friends and I can definitely say I currently have none. I imagine people might think I'm already busy or that I already have plans and that is the reason I don't get invited places, I just don't know how sure of that I am.. I have a ridiculous amount of people that i know and i seem to run into acquaintances regularly..Have you ever had a problem like this?? If so what did you do about it?? It just seriously feels like people think I'm already busy