At about 3 months I started to sleep with DS on my chest and got great sleep from there. Can't say it would work for you, necessarily. I found that the closer DS was to my skin the better he slept, so I took him out of his individual wrapping on top of the doona, to very light layers under the doona with me in the crook of my arm. Doing this regulated his body temp and mine and kept him more secure that I was there, so less stirring. My breath also regulated his breathing and meant we slept more in sync with one another.
You can read about this in Gentle Birth, Gentle Mothering by Sarah Buckley (she's a lot more scientific than I will ever be!), or I'm pretty sure Pinky McKay's website covers this somewhere (or else her books, which should be available in your local library network).
Buckley talks about the benefit to sleeping lighter, especially for babies (reduces SIDS risk because SIDS babies die in deep sleep, not light sleep).
It may just be that you need to make slight adjustments to your arrangements to make it work better. HTH