I think the best thing you can do is not think about it. I had a REALLY bad time with judging my own appearance and I realized that it was very unhealthy and it became a day-to-day habit. Needless to say, it drove me INSANE.

don't understand how I'm still single

What have you done to fix that? You can’t blame your looks if you don’t try.

Don't listen to those women at work. They know exactly why you're still single: because you're a provider, but not attractive enough to want to date. Otherwise, they'd be drooling all over you and trying to get in your pants. If they don't want to date you, but think you're good enough for "someone else", you got a problem.

Average isn't ugly, so it's not because of that. There are 2 other possibilities: you're either not fit enough (showing a 6-pack - by the way, it doesn't have to be a huge 6-pack, just enough to show, but I digress), or your confidence is somewhere underneath the floor. Possibly both. Losing weight and looking lean isn't good enough. You have to build some muscle. Your body has to protrude enough to make it look like you're a protector. They already know you're a provider, but being a provider doesn't give them pussy tingles.

When you lift, and get big, your confidence grows. One reason is because exercising itself creates dopamine. You feel good. When you look in the mirror, you look good. That creates that confidence boost, because as men, it's in our nature to want to look like we can kick some ass. When we look like a badass, we feel like a badass.

Women are very sensitive to the energy men give off. When they sense positive energy, they will react to that accordingly. If you're excited about something, they will be excited too. If you're confident in your masculinity, they will react to that energy and become feminine and submissive. When you're walking around feeling average and mopey, they will react to that too, and try to lift your spirits: "You're attractive. I don't understand how you're still single."

My advice is to spend more time lifting, and regaining your lost confidence. Don't worry about trying to become more attractive to women. Concentrate on building your body and confidence, and you will become more attractive to women naturally.

Don't reject yourself. Let women decide if they wanna fuck you or not. Play the game to the best of your ability. Fake it till you make it. And try not to take rejection personally - keep trying.

somewhat lean.

10% bodyfat is lean. You're probably still too fat.

I've had female co-workers and other random women tell me I'm attractive, and don't understand how I'm still single blah blah blah.

"How are you not single" is what women say to men they find attractive in a beta way. It's based on women who think that other women go for beta guys. Basically it is this: "Other women SAY they like beta males, you are a good beta male, how do these women who say they want beta men not want you?"

You know you are genuinely attractive to women WHEN THEY TRY TO FUCK YOU.

Ignore their words. Follow their actions.

Not to be too disparaging of you, I think you're probably attractive-ish, but not "fuck me now" attractive. Yet. But you can probably get there.

Personally though it's something I've never really considered, and believe I got a ton of work to still do.

You almost certainly have a lot of work to do: get lean, get muscular, and develop more of an attractive and compelling personality that does not involve being nice to girls.

I’m prolly gonna get downvoted for this but, LOOKSMAX till you get unsolicited IOI’s from women.