I suggest you think about what you used to do when everything was perfect. Try to recreate those happy times by going back. One problem, you sound as if you're changing too. That's what happens. One person changes and the other changes in reaction.
Fighting is destructive to almost every relationship.
I suggest you find out everything that is bothering her and see if you can straighten out the problems. Honesty and communication is called for here. Don't argue back. Don't defend yourself. Eventually you'll have the whole story.