Your doctor wants your son to weigh 20lbs at 5 months!? That's ridiculous! Mine didn't hit 20lbs till he was roughly 10 months old. Honey your baby's sounds like he's at a good weight! Just keep a good eye on him! You could always start the rice cereal. When my son started eating less formula that's what his doctor said. And he picked right back up on his bottles! We also had a bottle war at 6 months. Hes been drinking from a sippy ever since.
My son weighed 13.5 at his 6 month checkup. My dr said he was a little low on weight but she thinks there is nothing to worry about. We go Monday for a weight check . He eats good and is happy most of the time and constantly moving. We can't keep him still. I think he just burns off everything he eats. I think your baby is fine. 20 pound for a 5-6 month old sounds over weight to me.
My son is 12 months and weighs 20lbs. At 5 months my son was between 16-17 lbs. which is a completely normal weight for a baby of that age.
When my son was born he was 6 lbs 9 oz. when we left hospital he lost a bit and was barely 5lbs.
My son is in the 30th percentile for weight, but he is healthy and happy. The paediatrician says there is nothing to worry about :)
My son goes thru periods of time that he doesn't drink much either, but makes up for it other days.