Depression or laziness and disinterest?

I don't feel excited about things. I had been working with an organization for past 2 years, I quit because I wanted to pursue social media and writing, and have been working here for the past 3 months but I am not excited about it either. I don't even feel excited about sex. I am passive about everything. I feel tired all the time and often there's pain in my limbs and back. That may be due to hypothyroidism though but I take my medicines regularly. About suicide, no I never think about killing myself but I imagine death and how it should be. I keep thinking about going somewhere but when I do, I am not happy there either. I don't give my best at my job, I don't see the point. I feel lazy and I tend to forget things. I have low confidence level, and I get scared easily at work. I am worried about not doing well in terms of my career, I am worried about failing but I don't do anything about it either. I don't have any zeal to learn. I don't understand if I am just lazy.