Sleep Training

Hello, I have a 6 week old son. He is doing well with sleeping at night; this week his first round of night sleep is 4-6 hours, followed by waking up every 2-3 hours for next cycle or two. The issue is during the mornings and sometimes even through the whole day. He will stay up for 2-4 hours at a time, and even when he does go down sometimes the naps are only 30-45 minutes. Sometimes I think this is due to gas and fussiness, but more often then not he just seems to fight sleep. I really don’t want to spend money on a sleep course, since money is right and he sleeps good at night. Anyone have any advice for daytime routine that will help regulate him without messing with his night routine?