scared to put baby on his back!

[MYA2016]

My 5 week old baby (first child) has never yet spent a nap alone really. He is a very cuddly baby that's only happy in our arms so we have co-slept since the start when we realised it was the only way we'd get sleep.
I'm breastfeeding and he will sleep for 4-5 hours at a time over night and wake up for a 20 minute feed before dozing straight back off. It's working for us.
We have the snuzpod attached to the bed with a sleepy head in (he's not a fan yet) and a moses basket.
I'm very conscious of the fact that he's spending very little time flat on his back and I'm worried about his posture so we've been trying to introduce naps in the moses basket over the last couple of days.
However... Once on his back he seems to start gasping for air and making funny noises. He goes red in the face. He doesn't look in pain and he doesn't cry. But he just can't seem to breathe so we pick him up then he obviously wakes.
This morning he did it again. I was in the kitchen and heard him gasping, by the time I got to him he was coughing and looked like he was struggling to breathe. I quickly picked him up and as soon as I did he was sick.
he's never normally sick! Now I'm actually petrified to leave him on his back!
any advice? What could this gasping thing be, and am I screwing up his posture by allowing him to always be lying on us?

No you're not messing up his posture - the danger for babies is to be slumped in seats - as long as he's being held in a variety of ways you're fine.
I'd check with your doctor about the unhappiness on his back. It could just be he's it used to it , babies do love to be held, but could for example be reflux. Video it maybe so you have that to show them?

You should have your health visitor coming for his 6 week check, i would show her what he does. My son slept on his side from birth. He was breech and his legs were squashed up which resulted in him rolling onto his side, he would have his feet against the side of the Moses basket and slept like that for weeks. I was really worried about choking once he started laying on his back. Now of course he's nearly 7 months and has taken to sleeping on his front!!

It does sound a bit like it could be reflux. Could you put a folded towel under his mattress to raise his head a bit?