Breast milk is made from the child's demand. Babies won't drink more than they 'need' ie what they're biologically programmed to require for their growth. You're setting them up for life here. If he grew to be 6 foot 5 tall, it would all make sense.

My ds was born at 3.5 kg and then has been off the charts ever since. He was putting on a kilo in under two weeks and was in size zero at five months. Now at ten months he is growing out of size one and is over twelve kg. Yes he is heavy, but he crawls and furntu surfs and does everything normally.

The only thing that you need to worry about are your arms breaking from carrying him. I use a sling wherever possible.

Enjoy the cuddles!