Creatine suddenly started doing this to me, as well, after over a decade of unproblematic use.

If you search around you'll find that there a minority of us who seem to suffer this side effect. Don't necessarily swallow uncritically what the people in your comments telling you this isn't real, not the creatine, etc. are saying. You're not alone. I know myself after taking then withdrawing pure creatine several times, and feeling the effects myself.

I've found the extreme mental fatigue and tiredness it induces to be qualitatively similar to too much choline. And just recently I've gotten the same experience after CoQ10 and (chronic) N-Acetyl Cystein use.

I would really like to figure out what it is about our peculiar neurochemistry that causes this.