My son did the same thing til last week! When he was 5 weeks. I got a baby carrier. That helps during the day when I need to make food, clean, laundry, etc. Then, when I wanted him to sleep (aside from feeds and changes), I turn the lights off at 9pm every single night and don't bring him into a bright-lit room until about 7 or 8 am. I did this for a week straight and it did the trick. This may not work for everyone, but it was good advice I got from a friend. You can try white noise too. The TV turned up just enough to hear it on a station that doesn't work, or maybe a mobile with nature sounds, or even calming music. I use those whenever he's getting fussy late at night and it seems to work well. I know it's exhausting- I've actually lost weight because he wouldn't let me put him down long enough to make a meal! It gets better and easier though. Good luck!