Why the duck do I lose my mind like this after 'creative highs'?!?

I'm a hobby artist, and sometimes I have these mental, creative 'highs' when whatever I'm drawing ends up being above my usual artistic skill. It's just like a load has been taken off my mind and my head feels clear. They're triggered by music I think, and I love these highs. But the day afterwards, there's a f*cking aftermath! I am not kidding when I say it feels like there's a black, parasitic fetus in my skull, and it feels like my brain is growing too large, pressing against the bone. My sense of reality is short of gone, and I get panic attacks. This goes away way slowly, it takes weeks or even months at a time and I'm never completely free of it. Though they're usually triggered by music, sometimes they just get there for no special reason, and I've had 'visions' inside my head when it's at worst. I'm in touch with a shrink but currently I'm doing some sort of IQ evaluation that's taking weeks and right now I'm losing my god damn mind here! I'm not on any sort of drug, I don't even smoke. I just don't get WTF I am suffering from?!