Welcome you've come to the right place. Im 20 and I too am done with alcohol. I remember getting those bottles of nasty cider (they are so cheap!) and boy do they make you feel ill the next day.
If you'd like, pop over to the class of march thread, there are a bunch of us there all trying to stay sober (and mostly winning might I add!). Best of luck, i know how embarassing it can feel when you first realise drinking may not be a healthy choice anymore. You can do it