Can u check what email you used for your jsp acc somewhere?

Yes, you can log into your E mail account and check for an account verification E mail, but if you have deleted it, then you can change what E mail you want registered for D2JSP via the link that I have provided:

http://forums.d2jsp.org/settings.php?c=10

GL.

You can't, which sucks.

I don't know what email I'm registered to, but I'm 90% sure it doesn't exist anymore. Since I don't know it I can't change it either

Try email recovery then;
http://forums.d2jsp.org/recovery.php

Select the first option.

Be sure to include all the specific information that only you, the account owner, would know. The more evidence you have, the better!