Baby is a lazy breast feeder!

Help! My baby was 7-11 when born. My MIL bought me a infant scale. At 2 weeks old he is only back to 7 pounds. He was down to 6-11. I feel like he is such a lazy feeder at the breast that he is not getting what he needs. I do 20 minutes on each side but he quits sooner than that. He has plenty of wet and dirty diapers every day. As far as I’m aware my milk supply is good- I can always get an ounce per feeding using my haaka. At this point I’m tempted to bottle feed to get his weight up and maybe pump? Help!