First of all, pls no worries. As far as I know, there are two possibilities which can cause the double vision. On one hand, if you get the glasses not long time ago, you should check whether the prescription of the glasses is suitable for you and your eyes. If the prescription is too big, you will get the double vision while wearing them. If so, it is a piece of cake because you just need to change another pair of glasses. On the other hand, if your glasses have been with you for a long time, then I think you should go to hospital because it maybe caused by the astigmatism. Of course, if so, you just need to ask help for doctor then he will tell you what you should do. Good luck.