I think I’m depressed and I don’t know it

I work at a hospital on an evening shift (3-11pm) and my sleep schedule has been bad. I’ve been pretty good at waking up at 10:30ish and go to the gym until I have to go to work. The past couple of days I’ve been sleeping in until 12:30 and now it’s 1:00 and I’m still laying in bed, exhausted, and have to get ready soon for work. I’m suspecting I’m just really exhausted from my shifts and also for the fact that I’m going to bed at 2am. But this time is a bit different. I would catch myself zoning out while with my boyfriend and feeling sad, same goes when I’m with my friends. One minute I’m laughing, the next I’m zoned out feeling down. I feel kinda numb too. I don’t think I am ever happy. It’s kinda sad.