Oh god you are both so young. With a child also. The reasons why don't matter, you *have* a child so that is the reality you must deal with.
Are you both mature enough to want to work on your problems? Don't do anything rash right now, just take some time apart from each other to cool down (but don't move out). Tell her calmly you have a daughter and won't leave, that you two *will* work things out. Above else, don't argue with her and stay calm.
Ask her if there is *one thing* she would like you to do for her (except move out). Then actually do it. In the meantime, read this, then come back and post your thoughts:
http://www.marriagebuilders.com/graphic/mbi8111_leave.html
Second thoughts can generally be amended with judicious action; injudicious actions can seldom be recovered with second thoughts.
--Cyteen by C.J.Cherryh