i had the same problems. bear in mind that nursing releases hormones that help you fall back asleep and into a deeper sleep quicker, so try to focus on those hormones coursing through you and helping you get back to sleep. i found that i would be lying in the bed waiting for the baby to wake up again, which would completely not allow me to fall asleep. if you can sleep somewhere you can't hear a noise and know that someone will come get you if you're needed, maybe you can sleep. my method for helping me take my mind off things to fall asleep is to think of as many names that start with J as I can, and somehow i drift off.
with my second son, we slept together so he would nurse and we would both fall asleep. he was swaddled and i would put him on my chest to fall asleep, or he would lie next to me with his head on my arm which i had bent at a 90 degree angle to my body and under my pillow as well (not sure if i described that right) but he was right next to me, nose to nose. i could hear his every breath and somehow that helped me sleep cause i would fall asleep as he would and wake as he would too, and since he was right there he'd just latch on and i wouldn't have to get up or get back into bed. it was just us 2 in the bed, so i wasn't worried about my husband rolling on him. i was never worried about me rolling on him since i was such a light sleeper, sensitive to his every breath and snuffle.
i would say, if you decide to sleep with the babe, do not take ambien or tylenol pm or even drink very much. those things will make you sleep deeper and not be as sensitive to baby, potentially rolling on him. i took both ambien and tylenol pm while pregnant, but didn't need it as much after birth.
good luck!!!