Hi Susan, My son was also 8lbs 1oz born and weighed 14lbs 10ozs on his first birthday, so he didn’t even double his birth weight, let alone triple it (as is supposed to be the norm in the first year of life!).  He fell off the growth charts too and was totally uninterested in feeding and was even tube fed for a while.  He did however pick up over the next year and gradually worked his way up to the 25th centile by the time he was 4. He is now 18 years old and is currently 5ft 8" tall, which is within his genetic potential (I am 5ft 4" and his father 5ft 9"), although his bones haven’t fused yet so he still has a little growth left.  The first year can be hard but I am sure your son will pick up too, especially as he is under a good endo, so don’t despair!