One month checkup

My son just had his one month checkup this morning. I was really excited to see his weight because I feel like he has been breastfeeding much better than in the beginning. He was born 8 lbs 3 ounces, went down to 7 lbs 10 ounces at his first week appt. Then today, three weeks later he weighs 8 lbs 11 ounces. I thought that sounded good but pedi said he should be up another pound by now. So he is in the 14th percentile for weight. I suspected reflux a few weeks ago because he has many symptoms (which I brought up) and she first wants me to pump to see what my milk production is, if its normal we will look into the reflux or a dairy intolerance. Sorry this post is so ramblely, have any other Moms gone through this? I feel sad that he is "little" though she says he is healthy otherwise.