Co sleeping?

My son is almost a month old. 
We bought a little 'cosleeper' that we sometimes lay him in so he can sleep between us in bed. I find he sleeps better when he's just either laying on my chest or just laying there beside me. 
I'm absolutely terrified hell suffocate or something else will happen to him! 
But he rarely sleeps during the day. I have to constantly hold him and its wearing both my boyfriend and me down. 
Does anyone have some tips on safer cosleeping and a way to let go of my fears a little bit?