Well, be stupidly honest with her... be upfront and honest. Sit her down, with no distractions and tell her of all her short comings and how they're making you want to end the relationship.
Don't let this be an opportunity for her to just list back a whole list of your short comings (though no ones perfect and some of them might be caused by you).
From this talk you'll get to know if your relationship is salvageable, if she simply was unaware of how she was making you feel with her behavior. If she is willing to change herself, be more aware. Maybe you discovered something in your own doing.
But if it can't be salvaged and you both want to end it, just do it. Especially before you have any kids because that'll really have a negative affect on them and you don't want to put them through that.
All the best.
PS. No marriage is perfect, we all fight occasionally, try to salvage it first.