It’s normal as kids grow up and they become far more independent, for your relationships to with them to change. There will be strains, and it is common for them to become closer to one parent than the other. And it might switch over time. Or divide by certain aspects of your relationships. The kid may love to go to art galleries with you, for example, but wants to confide fears in the other parent, etc.
Keep the long game in mind — Raising healthy kids to be healthy adults, and take comfort in the fact they feel safe with each of you, but perhaps in different ways.
Yes, it can hurt a bit. Not going to lie. But it is normal.