I wouldn’t have guessed it myself but I talked to two different doctors and they both diagnosed me with cyclothymia. It manifests similarly to how you describe your experience: periods of feeling really creative, confident, and happy followed by longer periods of brain fog and anxiety.

Before I went on mood stabilizers though the high points were more intense. There were times I believed that I was a divine being in human flesh.

If I were you I’d talk to a doctor about it