Experiences like this are common, you are not alone. As I am no scientist or doctor, I can tell you, deriving from my experience, that pot is much more powerful than us youth, rebellious inspired neo-hippies like to think it is. It is just harmless we are told through all of the propaganda-powered forums and the web pages we surf upon. "It is medicinal, and is harmless...it's all in your head man!" are common responses you may get when asking these types of questions. But, if I were you, I would go to a psychosis/anxiety forum and ask about the Marijuana experience there. Chances are, you will get scientific answers to your questions. For this reason, and many others, I limit my pot like a hard-drug; only once a week at the most, 2 hits being the most I will ever smoke, and because of my prudent approach to this, I have avoided negative symptoms in as far as I can see. Don't get me wrong, some people just cant handle pot, while others can smoke them for years without any negative symptoms; the point being, technically when smoking weed, there is a significent gamble with your mental health you are playing, and the more you smoke, the greater chances increased. Just be careful thats all.