Help! Pumping to BF

Ok so! I wasn't able to breastfeed my first and my second didn't take either immediately so I pumped. However I found a shield that appears to work but now I don't know what to do once he finishes his feeds. Do I wait 30 minutes and then pump? Do I stop pumping?

I'm terrified of getting mastitis, that happened with my first. So how do I prevent it now if i start EBF after pumping since day 1? I also have an oversupply I think. For example, I nursed him tonight, 20 minutes and he was content and fell asleep. It was the same time I would have needed to pump so I wait 30 minutes in case he woke up hungry and then pumped. I still produced 10.5oz total. 🤷‍♀️

Also, how do I make sure my supply doesn't decrease while trying to breastfeed? Should be silly and demand right? I currently pump every 4 hours, sometimes he will eat every 4 or every 2 just depends.

I plan to try and only breastfeed tomorrow and see if he really is getting enough each time.

Any help is really appreciated, if like to keep my stash growing so I can get him to at least 8 months.