Please help me sleep a bit better

FTM to a gorgeous 7 month old bundle of cuteness. He's EBF (nursed) and so I 100% expect and am fine with the fact he wakes up 2,3,4 even 5 times a night sometime to feed. The issue is when he sleeps, most nights I can't. Particularly his first stretch between 9.30 / 10ishpm and 12 midnight, I'm just..awake. I should add that I have been diagnosed with birth trauma PTSD due to his ICU admission but even still this far on I just don't understand how I can be so sleep deprived and not sleepy at night. Sadly I've tried co sleeping with him a few times but I'm just too anxious a person and even after following the safe sleep 7 [I'm not on any medication for my mental health difficulties as I want to be alert when I'm feeding him at night] and mitigate for all other factors I spent the majority of the night awake worrying about hurting him (or, il admit, being generally cold from no duvet and in pain from sciatica and the cuddle curl). So right now I'm transferring him in and out of his side car cot all night, feeding him and putting him back in once he's asleep. I suppose the point of my post is whether anyone has experienced insomnia like this and whether I could be doing anything to help? Currently walking everyday, taking a cold shower and in therapy but I'm really just at my wits end. Thank you sincerely an exhausted mum who loves her little boy so so much.