Do NOT jump head first in the deep end like someone suggested. Indica may be great for anxiety, but it still is weed. Start small.

What really helps me out with my anxiety when smoking is to watch myself. Just observe yourself reacting the way you do. If I get too high, I just tell myself that I'll come down and try to laugh it off. Easier said then done, but with practice you'll learn. Something that meditation helps with. Just be more aware of yourself. You said you knew what was happening wasn't real, so use that as a jumping point. Next time something freaky happens, a strange thought or something pops up, just look it straight in it's ugly face and watch it. Laugh at it, even if you don't feel like laughing. That watching of the thought will create for you a space, a sort of bubble around the thought, so that even though it's there it doesn't affect you. And eventually it, along with the anxiety that it created for you, will go away. Kinda New Agey, but give it a try.