Dating a non-ace as an ace person... Yes or no?

Hey y'all! I recently entered my first relationship with a person who's not ace, and I didn't know (we started as just friends, so we never discussed that part really, even though they knew I'm ace). I know, I should've asked before agreeing, but I was too excited.

They said that they're not ace, they just don't care about sex being present in a relationship, which I don't quite get if I'm being completely honest. In my mind, you either want it or not. But I obviously cannot be in my partner's head.

But that made me rather anxious. I already feel like an incomplete partner. I don't want​ to consistently question the person I'm dating​ about that, but it's buzzing in the back of my mind nonstop. I feel like I made a mistake by agreeing to the relationship since I clearly have issues.

I feel like I should be grateful for being picked regardless, but also I feel like I​ can feel secured with only another ace.