A rollercoaster. It was dropping until the cheese thing, which I think is just normal, unspoken behavior. Sounds to me like a bout of depression, or at least what I think is depression. I 100% get the same lethargy to life, and it tends to come in waves.
If you haven't, I'd look at having a chat with a professional. I'm not a good role model for this, but I have pushed through the lulls more times than I care to admit, and it gets tougher every year. The negative thoughts set in and create this negative feedback loop that makes functioning difficult, and digs a hole that's hard to climb out of.
Anecdotally, if this is new to you, it doesn't make for a happy life. I'm working to get help, but there are roadblocks. I would encourage you to try the same. If it doesn't help, then you can cross that bridge later. If it does, then you'll be in a much better place and the light will shine again.
...or the Internet really is just shitty.
Ah yes, another cultured user. Everyone should know about and subscribe to Dropout.tv for the content and to support a solidly ethical company. Sam is a saint.