I'm scared/anxious about a lot of things now, I didn't use to be like this. What could be causing this, and what can I do?

I seem to be getting scared or anxious about a lot of things now, to the point of giving myself panic attacks. This isn't me normally, (normally I'm laid back to the max). I seem to get mad easily now and this whole thing bothers me. What could be the cause of this, and what should I do?