Hi, Uig, sorry to hear about your troubles, but at least you're realizing at a young age what changes you need to make.
I went to TCD too, starting drinking at 19, that was a long time ago. I'm sad to hear that there is still that peer pressure to drink. I was horribly shy, drank to fit in, made such a fool of myself so many times, didn't apply myself to my studies, could have done so much better, academically, and socially.
I hope you find a new social group, new hobbies, sounds like you're headed in the right direction.
I'm sure your folks will come around once they see that you're determined to make change.
Good luck, wish I had realized at 19 what you are now realizing. Your life will be so much better for it!