Need co parent advice PLEASE

So I’m having a hard time understanding how co parents co parent with a breastfeeding baby... like I’m going to try my hardest to pump and send milk because I’m civil but what happens if I can’t produce more than what I’m giving him??? I’ve already had a child and I was breastfeeding every hour there was no way to collect more. I’m nervous about over nights without me I’m nervous about everything with and infant 😞

Back story: I dated the man for 3 months before getting pregnant and when I was 16 weeks I found out the whole time he was cheating and was even on tinder meeting girls that’s why I’m even in this situation 😳 but all that aside I wanted y’all to understand why I don’t necessarily trust this person.