Baby with a low appetite?

My son is almost 11 weeks old, he’s been sleeping through the night since about 6 weeks old and since then his appetite has decreased significantly. He went to sleep at 830 last night and it’s 615 he’s still asleep. Before he went to sleep he took 4 oz bringing his total oz for the day to 16. He went to the pediatrician at 9 weeks for his two month shots and he’s already almost doubled his birth weight(possibly has by now, don’t have a scale at home for him..) and he’s grown 4.5 inches. But I’m concerned he’s sleeping 4-5 hours between feedings during the day sometimes? He used to be up every 3 hours like clock work during the day. He gets breast milk in a bottle I️ EP because he won’t latch. I️ don’t know if I’m just being a worry wart mom or if it’s something I️ need to talk to his pediatrician about? I just don’t think 16 oz a day is enough for him...