small baby and frustrated w weight gain.

Kelli • My wife and I got married in March 2015. We had our first baby together may 25 2016. We are trying for baby number 3!
Super frustrated. Our son will be 6 months on Black Friday the 25th. He was born a big baby, 9.03 lbs. in the 88th percentile. Well I wasn't gaining weight. I kept telling the dr. She kept wanting to wait and see. Finally when he had dropped to the 3rd percentile she said he was tongue tied when we had mentioned before. So we got that fixed. Had to pay 465 Bc who has dental ins on their newborn. That was 2 months ago. After the fix he got up to weight for a 4-5 month old. But now he's going to be 6 months and he's just barely 14 lbs. everyone just says he is small. I could accept that if he was born small but he wasn't. I wasn't a small baby either. Our donor isn't a big guy either but still doesn't it seem concerning ? He is breast fed and we started solids at 5 months Bc he was obsessed w food. He eats like 4-5 bottles a day and I nurse before and after work. So he's eating. He's happy and crawling. But I just am sick of being asked if he was a premier or how people say he's so little.