I think maybe its hard to know? I identified as ace for a few years before switching medications and realizing my old one suppressed libido and even desire... Its okay to use the label that makes you comfy and if it doesn't stick, thats okay too. If the lack of desire is bothering you, talk about it with your doctor. If you don't feel like anything is missing and it's just pressure to fit in, I'd say ace is more likely :)

god i ask myself this every day.. i’ve been having problems with being sexual with my partner only recently and I can’t tell if it’s my mental illness or if i’m just somewhere completely different, like asexual

Honestly, I have bipolar. So for me, there are times where I’m overly promiscuous and then there are times where I couldn’t care less about sex. It just depends. But I do feel that I can’t determine sexuality because of my mental illness

For me my asexuality has nothing to do with my mood. I can be super happy and having a great day but still not feel sexually connected. That never changes. I’ve never wondered if it was just depression because I’ve never experienced a day where I’m not depressed and therefore not asexual anymore. I’m always ace. Even when I’m happy.

This is so hard for me because mental health, medications, and physical health can all affect labido. I think its less about mood affecting your sexuality and more about underlying long term illness/medication affecting sexuality (such as depression). I'm sorry you also have this struggle.