Baby sleeping advice.

I could really use some advice from fellow mummies. I have a 9week old baby boy who struggles to sleep at night. I'm lucky if I get 2 hours at a time. And a total of 5 hours a night. I've tried pretty much everything I can think of to get him to sleep longer but nothing is working. What do you do to get your little ones to sleep longer? I've also found he does sleep better when he's on his side, but I'm scared to leave him like that while I'm alsleep too. Have any of you mummies slept your baby's on their side from this young? And if so how did you go about doing it?