My baby hates being on his back


My son is almost 10 weeks, we had a bumpy start but now we are thriving. To make a long story short because of him being smaller than expected, he spent quite a lot of time in my arms, and would be on his back only when he is sleeping. Sometimes he falls asleep on my shoulder and in my arms.

Anyway he is growing and getting heavier, so having him in my arms is not so easy. He does lie on his back for a bit but never for more than 5-10 mins max. I would like to extend that time. Any ideas that won’t traumatize the both of us or his nanny