I just googled a ps4 friend to find out more about them, is this stalking?
Oh no you didn't. Why would you? How could you? Did you find out anything about them?
I found out he had a very tough childhood.
It is okay to be curious but you shouldn't try to find out about them by stalking them online. It will feel like a betrayal to the friend and could end your friendship.
I'm not sure if he'll trust me anymore.
He might not know, so from here on out, don't allow your curiosity to get the better of you. If you want to learn more about someone, just ask them.