Toddler won’t sleep in his own bed

I feel so guilty my son has co slept with us for a few months was brilliant in his cot slept through until I found out I was pregnant we needed his room for nursery so did the bigger bedroom for him with a toddler bed he hates it he has slept with us for around 6 months now. My baby girl is 7 weeks old and hubby goes back to work tomorrow. Last night my son fell out our bed whilst we were down stairs with the baby and ended up being sick an hour later with concussion. I was adamant he was staying in his own room tonight! Fast forward tonight my partner does bedtime lets him fall asleep in our room I try to transfer him he wakes he’s crying for half an hour screaming made himself sick now he’s cuddled up to me in our bed… I feel so helpless. We have been taking it in turns one in our bed with our son one downstairs with baby girl all night in Moses basket. I just wanted to try all of us upstairs and him in his own room tonight and not worry about him falling out of our bed if we’re not there any advice? Thank you xxxx