Story about two best friends convinced they’re aro, but have simply been in love and in a relationship since they were kids

I'm looking for a book where the main couple has been best friends and doing all the relationship stuff for years. ie kissing, getting freaky, going on dates, cuddling, but are convinced it's just because they're such good friends. And they think they're aro because they've never had any interest in anyone else.

It's not at all a requirement the genre itself be romance. Just that this dynamic be present