AIO for feeling like is over after my youngest turned 28?

For context I’m 42, had my oldest child 18yrs old, and had 3 more kids every 2 years. My youngest child recently turned 18 & graduated high school. My other kids are in college or married with one living a home only for the summer & breaks.
I have been mentally crashing out, randomly crying, and feeling my heart beating out of my chest thinking about not having any “kids” at home. I’m spiraling, but doing my best to not show emotions about it around anyone.
I’ve tired to talk with my husband about it but he doesn’t think it’s a huge deal.
This could be where I’m overreacting……. He’s mentioned we get to do whatever we want, and I can get some hobbies since I never really had any due to having kids so young.
It makes me so mad to hear him say these things to me each time. I feel so dismissed and honestly I’m crushed this seems like a tiny situation to him. My whole identity has been being a mom.
So AIO?