I had an iodine deficiency! I wasn't eating dairy or eggs, I was cooking my own food from scratch, and I was using sea salt instead of iodized salt. In addition, I like drinking alcohol which makes it harder to absorb iodine. Felt like shit. Couldn't muster the energy to give the slightest shit about anything.

Got blood work done and found out. So I started taking a supplement every other day for it specifically because I'm just not getting it in my diet. I'm feeling pretty great now.

I don't think supplements are generally the answer, but having a work up done and learning some shit about yourself can be pretty eye opening and point you at what you need to do to fix your diet. It's a good first step, but not a magic bullet.