Often anxiety and stress can manifest in different ways.
If my husband has a lot on his mind with work/stuff on at home, he'll tell me he's "not stressed or anxious" but I'll notice he'll develop a new obsessions.
Here are some recent examples:
His health. Various ailments over the last few years which have all been checked out by doctors and turned out to be very innocuous things. Like indigestion! These tend to develop when he's visiting another country on his own for work, or he's due back at work after a break (and has a busy month ahead).
Wasps. He has spent hours watching, viewing and researching wasps nests. We have had wasps in the roof and I wasn't bothered because you call an exterminator, pay the fee and it's dealt with. No biggie. (We did this last week and it was a 20 minute job). He obsessed and obsessed over the wasps. But I'm not daft. It coincided with our 12w scan at the hospital for baby after a loss at our last 12w scan. So I knew that's what he was really worried about.
There's more. But I won't bore you any further.
I'm also the same but I noticed it a few years ago. Oh, my latest obsession with X is because I'm really subconsciously worried about a big job I've got to sort. I went to hospital for tests twice or health conditions I convinced myself I had. Daft when I look back on it.
All of that to say, your traumatic birth, going back to work, even work stresses and stains themselves... they could all be causing your anxiety about your child. In fact, I'd put money on it.
You are not your thoughts. Don't be taken in by them. Your brain is telling you wrong and you need to rewire it.
Mindfulness is great for this. Simply look at your child in a single moment (at the breakfast table or enjoying the swing on the park for instance) and instead of worrying that it'll be taken away, think "no, I don't need to worry. In this very second, at this exact moment, my child is happy, healthy and having fun".
It should help!
But I'd also talk to your GP or HV if you haven't already. They won't bite and they see this all the time.
Good luck and I hope you feel better soon.