Growth percentile chart?

Brittney
My son went for his 2 month check up today, he is now 10 pounds 1 ounce! Great right? Wrong! In the two months he has been here he has only went up in weight a little bit. Started out at 7 pounds 12 ounces dropped down to 7 pounds 3-4 ounces before leaving the hospital failed to gain weight for the longest time. About 3-4 weeks in he started to slowly gain his weight back. According to his doctor his growth percentile keeps dropping, he is now in the 5th percentile for weight and dropping in the length. When he first came in he was 20% for length now he is 9%! Like seriously what is going on with my child? We was told yes he is gaining weight but it's not as fast as it should be. I'm doing everything I can to get him to gain the proper weight, i just don't understand where I'm going wrong! We go back Monday for another check in his weight/height, if he does not go up on the percentile growth chart we will be doing blood work to see what's going on. Also we may have to change his formula, problem is we can't seem to find a high calorie hypoallergenic formula. 😟 This is seriously the MOST frustrating thing to go through. If we can not find the proper formula we will be adding Kayro syrup (yes I'm aware I spellt that wrong!) to his bottles. 😐 please tell me I'm not alone? I know I probably am but it was worth a shot to find other moms going through the same thing we are going through. 
Edit: I'm not sure why this posted anonymously! 
He had he has had numerous weight checks since 6 days old. He was EBF for 6 weeks and failed to properly gain weight in those 6 weeks. His percentage keeps going down and has been going down according to the doctor.