8 week old loss of appetite?

Tammy

Anyone else? My lo was having 6oz every 3hrs then Thursday last week had a bit of constipation which has gone away over the weekend with the help of extra water tummy rubs and lactulose medicine however hes now only having 4 1/2oz every three hrs and sleeping after every feed whereas before he'd stay awake for half hour after.

Another growth spurt? Or should I be worried?