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.
Firstly you are supposed to check if the double vision comes from only one eye or both eyes together. You can looking at a light with closing one of your eye to see if the light is double. If you see the light is double, it means your eyes are normal, but your glasses are with poor quality,..you need to change another ones.
But if you see double only when both eyes are open, this means you have got a vertical double vision (diplopia), which can be caused by the lenses' poor centration or a wrong prescription, or it means you need for vertical prism in your glasses.
Seeing a doctor is suggested for you though.
Temporary episodes of double vision can happen for many reasons, including drinking too much alcohol or being overly tired. This type of short-term double vision is usually not cause for worry.But if the double vision is long-lasting or keeps coming back, reasons for it can include stroke, head injury, brain tumor, brain swelling or brain aneurysm,corneal irregularitie and so on.