Baby eating habits

My baby is 8 weeks old and I’m worried about his eating habits. For the past week he’s only really wanted to breast feed even at night. I have given him bottles at night since he was born and he was gaining weight steadily. Here lately since he’s only wanting to breast feed he only eats maybe 10 minutes and I feel like that isn’t enough. I’ve been waking him up during the day every hour and a half to feed but I feel like he isn’t getting enough even though he seems satisfied. He has a doctors appointment on Monday and I plan on bringing it up but if you guys have dealt with this what did you do?