Newborn jaundice and feeding

My baby boy got newborn jaundice on the when he was 2 days old.

I was produced enough colestrum and he had already pooped. So when he got jaundice, the midwives insisted that I top it up with formula so he can recover. He had to get phototherapy. And that it would be easier to feed him while he is under the light. I tried pumping cause I planned to EBF but hardly got any. My milk hadn't come in. Post partum depression took over i cried like crazy and had to than feed him formula.

5 days old he came home. But he still has it, I need to feed him enough so he gets okay. I have been producing enough, I can express 60ml from both boobs. And he drinks it all. But when I nurse him I'm not sure if he if taking enough. I feed him after every 2 - 3 hours.

He poops frequently, mustardy seedy poop. Enough wet nappies too.

I'm a FTM and worried if I am on the right track. How do I know I am feeding him enough and that he is gaining weight?

He is 9 days old