I remember those days, when my baby girl was that young, we sometimes had to rock her to sleep, or at night, I would watch TV late at night (very boring, when all there is to see is those stupid game shows). Try & resettle you baby boy in his cot, ie patting him when he is lying down & a good wrap doesn't go a stray either. I was also recommend a DVD "Happiest Baby on the Block" which seem to help wonders at that age, by 12 weeks our little girl was sleeping 7hrs at night. But unfortunately that only lasted until she was 6mths old , now we have other issues. If I could do it all over again, I would definatley resettle baby in the cot, try not to get them out. But of course make sure he is fed & has had nappy change. Oh one thing with the cooler weather, you may like to heat his cot with a heated pillow (those ones you put on sore muscles) then remove before putting baby in, this helped wonders to.
Don't worry it all gets better, then there other things that test the mind. However enjoy looking after your newborn