my baby also lost over 10% of his weight during the first check up at the MCHC, but i did not give formula in every meal...but you need to wake baby up every 2 hours and make sure baby eats both sides of your breasts at least 20 mins each side!! if baby goes to sleep, you should wake up baby.
and for mothers, you should drink 1 cup of water BEFORE feeding and 1 cup of water AFTER feeding!!!! if you want to increase your milk quicker, you can pump 15 mins each side AFTER feeding.
and you can also drink herbal tea that increase breastmilk or take supplements along with the above technique...that's how my baby started from the 55% line to now 85% line!!! add oil~~