I used to get it when I got super high my first couple of times. Usually in my legs though, made it hard to walk, but I found if I just got up and moved around, or didn't think about it and chilled I was fine. So I guess if it really bothers you stop smoking. I think if you smoke less and just get a nice chilled out buzz rather than getting blitzed it could help as well. If you can smoke more sativa and less indica as indica strains will lead to more of a the physical stone, and feelings somewhat similar to what you are having. Anyways good luck, and don't worry about it too much, if it's only when your high I don't think its a tumor, stroke etc.