SUBREDDIT: r/relationship_advice
TITLE: [22/m] I may have found the perfect girl for me[20/f]! Only problem is, I already have a girlfriend [20/f].
POST: I don't know what to do! I've been with my girlfriend off and on for the past 3 years. It's ben a long distance relationship for the past year and a half when i left for school which has been really hard for both of us. we broke up for about a week in september but we patch things up and have been doing really well since then. The other day, I met this girl who just really, really gets me in a way i don't think my current gf ever will. We've been texting pretty much nonstop and flirting a fair amount (she doesn't know i have a gf) and she seems pretty into me. We haven't "done anything" yet and i don't want to be a cheater so its seems that if I want to see where this thing can go, I'll have to break up with my gf. I still care a lot about my gf, though, and i really don't want to hurt her. I've never dumped anyone before, i've always been the dumpee so i'm kind of in uncharted waters right now. How can i break things off? should i do it in person, or over the phone? Am I making a huge mistake? Help!
TL;DR: 
been with a girl for 3 years, met a new girl who seems to be a better fit. inexperienced in the ways of dumping, need help.