You have to understand, like you said, cannabis isn't for everyone. The real question would be why you're getting paranoid, and removing that variable would probably give you better results. I'm not sure what you mean by blacking out, as I've never experienced this myself, but maybe you're just reading too far into your high.

There's not medical reason for what you're going through, and don't believe what you learned in DARE, because one hit isn't going to kill you. Just take it easy, don't worry so much, and above all, just try to have fun.