What changed in the past few weeks? Look at this as possibly a somatopsychic issue. Look at dietary changes or other health changes. But also look at other stressors, like breaking up with your SO or having a falling out with a family member. Depression typically comes from one of two sources: 1) wonky brain chemistry, which is a medical issue or 2) some kind of real world problem that leaves you feeling helpless, often that problem is social in nature.

Best of luck.