Ihave really mild short sightedness and wass given a prescription for glasses that i definatly have to wear for driving. If i dont wear my glasses often could it make my eyesight deteriorate?

If you are young using your glasses will make your sight WORSE. Only use them when you have too EG Driving

no
but dont crash the car eh?

yes your sight will get worse

No, but it would be silly not to if you need them.

Well I was prescribed glasses that I 'must' weat for computer use and reading, then I had another test today and they said that I definately don't need to wear glasses. I asked her if she was sure because of the previous prescription but she said definately!

Yes it could I wear glasses all time I am short sighted too.