Well if you weren't going back to work, I would say just keep doing what you're doing! We did that with my son until about 5-6 months...then we were really sad when he got the "jimmy legs" and needed his own space to sleep in. So we were forced to move him out of our bed. Since you have a time line you're going to have to start being firm though if you want that transition to be smooth for him. Try thinking of ways that you can slowly offer less of your presense. Like lying next to him and patting his back but not letting him snuggle close. Or rocking and holding him, but laying him down while he's not quite asleep. I would encourage you to read the "No Cry Sleep Solution". She is a big advocate of attachment parenting and sleeping with your baby, and has some really great suggestions for parents transitioning out of those kinds of sleeping situations. But honestly, 6 weeks is really really early to begin sleep training in my opinion. I wasn't comfortable letting my son "cry it out" until he was 5-6 months old. At six weeks they really need to be fed on demand and held as much as possible, for their development. If you have the freedom to really pick and choose with a daycare, see if you can find one, maybe a home daycare or something, where you can actually request that someone hold your baby as much as possible. Even offer to provide them with a sling or other kind of baby carrier. That holding and physical contact is so so important early on. If he can't get that during the day though, you can continue to do those things in the evenings and let him sleep with you at night to get that contact he needs. He will eventually learn that during the day he will have to sleep on his own and at night he gets you.
And now that I read everyone else's solutions...I agree!! With the swaddling. Read up on doing it just right, very tight. We still pseudo-swaddled my son even when he didn't fit in it...it was more like a straight jacket just around his arms...he looked so funny with his legs sticking out. But he loved having his arms tucked down and snuggled tight. I bet swaddling will help you a lot!
love and good luck,
Missy S.