DS 6mths was the same a few weeks ago, so you have my sympathy.
We found a combination of a nice warm bath just before bed, raising the mattress with a pillow, coating him from head to toe (well, almost!) in snufflebabe (including his back, between his shoulder blades), a bib tied to his cot rail just out of reach with a few drops of baby olbas oil, all seemed to help a little.
In the end we took him to the GP because the chesty wheeze went on and on for weeks, the GP wasn't overly concerned as apparently it's quite common, but did prescribe him an inhaler which has also helped a lot when he's been particularly bad at night.
Also a life saver for us was the NoseFrida - pop a few saline drops up the nose, let them soften the mucus, and give the tube a good suck - it's amazing how much gunk collects in the reservoir...
At his worst, DS did sleep better when he wasn't flat on his back so we did let him stay asleep in his bouncy chair or his car seat, or on one of us, if that's where he fell asleep - it certainly wasn't worth waking him to put him down in his cot.
I really hope your baby gets better soon - in the meantime, and 
for you x