Baby boy

My baby boy was born just under two weeks early (today being his due date (6/7/2018) born 5/26/2018) He was born weighing 6 pounds 8 ounces and went home weighing 6 pounds 4 ounces. Which is normal. At his first pediatrician check up he weighed 5pounds 12 ounces and she was concerned about him losing more than 11% of his birth weight. Fast forward to his next check up he was exactly the same weight of 5 pounds 12 ounces... he has another recheck today hoping he gains something!! I’m breastfeeding and am worried that he just isn’t getting enough. He has plenty of wet and dirty diapers just isn’t gaining!! I have switched up my ways of feeding. He is getting offered the boob every 3 hours weather he wants it or not (usually every 3 hours he does but every 2 hours is too soon and he fights) and I offer it if I hear his food cry! While he is on one boob I put the haaka on the other and then whatever I get from that I feed him from a bottle. He seems full but isn’t putting on weight!!! Does anyone have any suggestions. I really don’t want to switch to formula but if it benefits him I will. 😢 I just feel like I’m failing him!!! 😢😭🤱