Help no sleep

My baby is 6 weeks and 2 days he isnot sleeping through the day maybe 15 minutes and wakes up again and he's been really cranky because he's sleepy but he's fighting his sleep He was doin really good before he was sleepin during the day and at night would have the last feeding at 1130 12 and not wake up till 330 4am them again at 7 wake up but it seems this day schedule he has taken on is messin up his whole schedule what can i do?