baby weight

Tess
My baby was born at 5 pounds 12 ounces, spent 9 days in the nicu with pneumonia, and left at 5 pounds 6 ounces... he's now about 10 pounds, 2 and a half months. I just feel like he's not big enough. He eats about 5-6 ounces every 3-4 hours during the day and 6 hours at night... I'm just tired of everyone saying "ohh he's almost 3 months, he's still so tiny". 😞 I feel like I'm doing something wrong. I'm trying to up my breast milk supply. He currently gets 1-2 breast milk bottles per day. 
Is that a good weight gain? 
He goes to the doctor in the morning but I just want to know other moms experiences.