i dont know what to do

today me and my fiancee split up. we were together for 2 years a 6 months. we also have a 6 month old little boy that is my pride and joy. me and her have been having our differences and arguing for a while now. we separated 6 times in a 2 week span before this. weve been arguing for a few days and last night she said she was tired of me, so i said im tired of her and ended it. i told her i was done for good.
as of today she has been begging me to get back together with her. i love her with all of my heart and more, but i just dont think that it would be the best decision to get back with her. we have been through so much, but at the same time i dont think that its enough to fix us. she keeps saying she will do anything for me, but i answer to her: why now?
why after all of this does she want to change? because she lost me? its happened before, why now?
i just dont know what to do. im only 17, im in such a dazed state. please dont judge the age. its hard being this young with a child and maintaining a relationship. please help