Thanks to MKitty and AbbyMom for your replies

I took him to the vet after work tonight, but had to leave him overnight since it was near closing time (I miss him).
He is also being checked for a UTI. He seems to potty a bit more than normal and from what I understand, an infection can sometimes cause seizures.
The vet also mentioned diabetes as a real possibility- quite common in cats I guess, and treatable like you mentioned.
I am almost hoping that it's one of those two things because any of the alternatives would not be good.

Hopefully I'll know more tomorrow. Keeping fingers crossed.
Thanks again, and I'll post when I find anything out.