My stbxh had exactly these feelings, unfortunately it's why he is a stbxh.
Like a pp said, these feelings are in your head - which doesn't make them any less difficult to manage, but does mean that they're not necessarily reflective of reality.
Do you get this way about other things? It can be worth speaking with your gp about depression and if possible speaking with a counsellor, NHS wait lists are huge but many companies offer this via an Employee Assistance Programme, maybe via health insurance or even privately, counselling is a lot cheaper than divorce. I understand you want to talk to your partner, but she has her own burdens too and these kind of discussions are really hard to. There are also some really good parenting courses that are still running online, often your gp can refer you or your local council may have parenting support. It's a great chance to talk to other parents in a really open and honest way, to learn from each other and also see the real challenges behind the cosy Instagram pictures.
The other thing that my DH never managed was to get out of his own head and focus on the rest of us and our needs. I always felt so upset that if he had been able to just look up he would have seen that I had my own concerns about my parenting, that our young DCs love and need him and that he brings his own wonderful self and skills to being a parent. This also meant he never managed to integrate the children into the life he wanted to lead - it's harder when they are young, but you can find things you both enjoy. For example my dad is never one for playing much with kids but he loves woodwork and has happily spent so many hours teaching his own kids and now grandkids how to hammer and saw and make cool things. Or my brother loves cycling, so from little he'd take his kids out in a bike trailer whenever he could, and now he and his daughters mountain bike every weekend.
I really hope you can manage this. It's been a sad journey for us and even sadder because so unnecessary - but you are not alone, many others feel the way you do.and manage to turn it around.