University Problems???????

I am at uni and everytime the student union has a party which is usually every week all my friends get drunk and get off with the nearest random guy and I just wanted know why, Im not like that at all tbh and makes me feel so uncormfortable when im left on my own when they all wander off without me and I end up just going back to my room. Also my friends keep badgering me come out when I dont want to, I dont mind going out and partying and that stuff its Im not one of those ravers who do it every night and when they finally give up trying to get me to come out they are always funny with me about it, any thoughts?