No sleep

LO is now 8wks old and I am still only getting at most 3 hours of sleep a night. I am EBF and always make sure that he eats longer before bedtime, I have even tried give and oz or 2 of expressed breast milk to top him off. He is perfectly content sleeping but as soon as I put him down flat on his back he begins to fuss. He sleeps in a dockatot, when I purchased it I thought it would be comforting to him due to the fact that it seems to hug baby on the sides. I have tried placing him in his bassinet and he rolls onto his side, his dr is not ok with this so I then roll him back to his back and 2 mins later he is once again on his side. I am at a loss for what to try next and his dr seems to be of no help, she just states back is best. Any advise would be much appreciated, I am not sure how much longer I can function in what my husband refers to as zombie mode!