did smoking cannabis give me anxiety and will it ever go away?

I'm nearly 17 now, and I started smoking cannabis heavily when i was 15, up until about a month and a half ago or something.. It got to a point where every day i got so scared about death.. and silly things like nuclear bombs dropping nearby. I was angrier too, I was much more confident to speak out when something had pissed me off, but never said anything in the right way. I got so paranoid about my health and thought i was gonna end up dead and being trapped in a place where i can't escape. So when it got to that point, i walked away from the friends that encouraged me to smoke weed.. they don't speak to me anymore now. I'm trying to concentrate on things that i'm supposed to be doing. I'm taking St johns wort to try and calm me down a bit and it has definitely had some effect.. but everyday i still have negative thoughts in my head. I've got bad sleep disturbance problems, i've ended up going to the hospital so much because of health scares but i'm being told constantly that it's my anxiety, yet i still worry? It's been around a month and a half since i was smoking weed, but i still find myself anxious, and i used to be so positive when i was younger, but i understand that i've kinda messed that up now.. will this anxiety ever go away? am i gonna be stuck with it forever?