Is this manic depression?

Ok so I have a good life, I've had to work a lot and almost been homeless a few times, had family be nasty to me etc as everyone has, but I'm settled living in a nice flat and I can live off what I make now and have a few friends. I'm a happy person who always works hard and tries to be optimistic even if life seems to want to run me down. I've been fine for years.

However, for some reason since a few months ago, about once or twice a week, I wake up in tears feeling super unhappy. I can barely find energy to move, and I cannot eat but I can drink water. I feel like magnetized to the floor, and have panic attacks but they come and go. The rest I just feel stuck to the floor, heavy and can't stop crying. It can last an entire day, or a few hours.

I've never felt like this before, I'm always so happy and energetic... why is it suddenly happening now?