This is a difficult one because long term marriages or partnerships most definitely ebb and flow through different stages.
Stress can absolutely be a leading factor in feeling separate from your partner, especially the stress of having young kids - when something or someone is demanding so much utter need from you, you can sometimes feel as though you have zero to give. It can feel as though you’re treading water just to keep yourself going, let alone worry about yet someone else and nurturing a relationship. And when you’re not in sync, it can feel like your partner is a barrier to you just getting through the day. I think this is all more prone to happen when your partner is also feeling stressors. You just can’t look after each other.
Saying all that, even when all the above may be happening, it should probably still be the case that you still feel deep-rooted love for them and look forward to better times ahead and WANT things to get better.
What’s the context of these worries or lack of feelings? How do you feel in yourself day to day?