I want full custody of my son!! Please give advice!!

I want to file for full custody of my son, but am nervous that I wont get it because I work a lot of hours (53+).
I left my son's father 6months ago and we chose not to go to court and had a mutual agreement notarized.
We had plans of getting married and had purchased a house together, although the loan is in his name. I moved out since moved into a very nice 2 bedroom apartment, have gotten a new job where I now make more then my son's father, and I have been in school full-time for the past few years and recently switched my classes to all online so I could have more time with my son.
Im just nervous because of my work schedule... I would be willing to change my job to one with mothers hours if I was receiving child support.
Any type of advice or thoughts would be much appreciated.

Thank you!