Most Helpful Guy
If you wanna be with somebody else, you should really broke up first with the oher person first. she deserve it.
I can't tell you if you'll regret it or not.
Never cheat on somebody. there is nothing bad to broke up, but cheating will hurts him/her, plus everything you do will happen to you to :)
Most Helpful Girl
Prolonging the break up can cause problems in the future. If you like someone else, you like someone else. Not breaking up now, can possibly cause you to have resentment towards your girlfriend. It will save you both a lot of hurt just doing it now.