Input on how much formula...

My baby is 7 weeks 4 days old. For 3 days now, I've been feeding him 4 ounces every 4 hours for the most part. Sometimes he'll take 3 every 3 hours like he used to and when he sleeps and wakes up (I feed on demand as advised by his doctor) he'll take 4 ounces again and it's back to 4 ounces every 4 hours. Am I feeding him too much? I started giving him 4 ounces every 4 hours because I noticed that after giving him 3 ounces he was still hungry and I made him another one and he drank it and fell right to sleep.. I was commenting to one of my friends about it. She's not a mom but her friend is and she spends a lot of time with her and says that her friend's baby who is now 8 months old was fed 3 ounces every 3 hours until he was about 6 months old. That her friend's pediatrician told her that that's the age when babies are supposed to be fed 4 ounces every 4 hours. Mine still goes back and forth, depending on how hungry he is. Am I feeding him too much? Of course I don't want my baby to go hungry, but at the same time, I don't want to over feed him and possibly causing him tummy aches from being too full. 😞 I was going with my gut feeling about how much he should eat. Because I did read that if he eats 4 ounces, the next bottle should be 4 hours after that. Like I said before, I feed on demand and when he does take the 4 ounces, he'll show signs of hunger 3.5 to 4 hours after depending on if he drank 3.5 or 4 ounces.. Her telling me that just worried and confused me. I don't want to unknowingly hurt my 7 week old baby's stomach thinking I'm doing the right thing by feeding him like that 😞 but then at the same time, he seems content and goes right to sleep after he eats and if he doesn't want some, he'll spit it out and that's how I know he didn't want the full 4 ounces so I really don't know what to think. It just confused me a bit.