Your facial expression is always a perfect representation of your mood, I used to suffer from depression, lived in solitude and cut my self off from the outside world, suppressed all of the real desires i had and tried to cover them up by staying in playing video games and eating all day telling my self i don't really want go after my true desires and live my dream life.
After many years of this i began to realize its impossible to truly irradiate your deepest inner desires and EVERYTHING you do to try and mask them leaves you living an unfulfilled mediocre life.
I used to be the guy that looked unapproachable, felt like everybody in the world was negative and selfish and it was all their fault that deep down i wasn't fulfilled. It wasn't until i said enough was enough i needed to change myself not anybody else that the world outside also began to change also. I went from being the moody unapproachable negative person to, extremely confident, happy, playful, funny dude that people genuine enjoyed being around, I couldn't see it at the time but looking back from my current perspective its so easy to connect the dots and see how your attitude and perspective on life massively effects how you interact with the world, the conversations and people you meet. I can now see people who were in my shoes, moody,negative no confidence and not actively doing what they truly desire and love to do and see how unattractive to other people that makes you, The only people that want to be around other negative people are negative people, positive happy people just don't want to be around them.
If people are truly noticing you look moody all the time, i would honestly with all due respect be honest with your self and ask yourself if you are truly happy and fulfilled? If somebody in my family told me i was moody all the time which they wouldnt anway but if they did a happy person would react with surprised smile like lol wtf what are you on about everything is good! if you react negativley in a moody way like whatever just leave me alone that suggests there is some truth in their observation.
thats another thing i now see with depression while your in the mist of it sometimes you are not even aware of it! or you are in denial you just think its normal for life to be dull and boring.