You have to quit thinking about 'them', and do what you need to do 'for you'! Being weak and pathetic, begging and crying...that ain't gonna make them change their mind! Period! This is a situation where you have to do the opposite of how you feel. It's hard, but you've gotta do it. You gotta start thinking about you, learn, become a better person and a better parent and a better partner...and get stronger. They 'might' come back...then again, they might not. But, you will be better off by being stronger and by being a better person, a better parent, and a better partner...if they don't come back. You will feel beter about yourself either way. It feels counter-intuitive to do these necessary things...but you have to do them! You have absolutely no control over their thoughts, feelings, or actions...so don't bother trying! You do have complete control over your own thoughts, feelings, and actions though...so exercise the control that you do have! This is hard stuff, but other people 'do' get through it...over time...and you will too! I'm sorry for your circumstances...but you CAN do this!
"Always go straight forward, and if you meet the devil, cut him in two and go between the pieces." - William Sturgis, clipper ship captain, 1830's.