I've been in a relationship for over 4 years. I met her my sophomore year in high school, and we started dating my senior. Things were going swell for the first year of the relationship, but for the past 3 years has become progressively harder with her moving off to college. We have both broke each others trust in the past three years and are always arguing or under each others skin. We have been working on things but several months ago I met someone else, and she's been weighing heavily on my mind. I like this girl but, I don't know what to do...

Disclaimer - With this answer, I am assuming that there is no marriage or children involved in this situation.

Follow your heart. You cannot find the right one, without letting go of the wrong one.

Have you considered breaking it off with this girl and finding a relationship with less complications and drama?

So you've had 1 good year and 3 bad ones in a long distance relationship? I'm amazed it's lasted this long. I'd ask her if she's serious about this or just hanging on just because it's easy to do at this point. If she's not seious about fixing any issues let her know you'd like to move on as you are starting to enter a new stage in your life and you don't see the relationship as working long term under the current conditions.

Before you cheat, break up with her like you should have done 3 years ago.