At 6 weeks, I would be almost certain he needs before noon. When DS was 6 weeks he could stay awake for about 1.5 hours and would then nap for 1.5 hours. It is VERY hard at first to get used to their signals and tiredness can easily be mistaken for hunger. I would perhaps try and put him down after 1.5 hours regardless to see if he will sleep. Prior to that I would have really quiet activities to reduced the risk of overstimulation. By the way, at 6 weeks, I was only just starting to put him down awake. Before that DS would often fall asleep in my arms and then I would put him down when he was asleep. Perhaps, if you are putting him down awake, he is crying because he doesn't want to be away from you, not that he isn't actually tired. Are you swaddling? It really helped my DS to feel more secure.