I need to admit to someone that I've been cheating on my girlfriend for a year
Are you joking? Did your partner do something to make you feel it's okay to cheat on them?
Not really, I decided to go out with practically any girl at this point. Life is too short to be with only one person.
So, your mindset isn't wrong but the way you decided to go about it is terrible. You just shouldn't be in a relationship at all because you and I both know cheating is wrong. Break up with your current partner before you do something like that.
I don't care about your opinion I just wanted to get it off of my chest.
I'm sorry that you don't see the problem here. You need to let your girlfriend know about the way you feel, so she can move on and find someone who can be faithful. It's clear that you want to sleep around at this point, so just let her go.