Does anyone know if it is normal to worry about everything?

I feel as if I am worrying too much about things. I have always had a habbit of thinking too much and obsesssing over everything. As a child, people said that I would over-think everything. I have come to a point now where I feel ok for a period of time, but every week or so I get this period of thinking about a problem to the point of breathing faster, not being able to sit still, shaking and feeling as if the whole world is collapsing and I just have to escape. This is usually followed by crying and a period of calming down. Sometimes if I am really scared, I feel like I am not real, like I am in some kind of video game. Mostly, I often worry about feeling lonely or worrying that I am going to die.
Does anyone else ever experience this and is there anyway that I can help it?