i wouldn't have thought that it would be the cider, teeth can become senstive when teh enamel thins, this could be caused by the cider because its a carbonated drink and is acidic which can cause the enamel to dissolve a bit, you could havea buid up of plaque which is causing tot o hurt, or something else, if you do have worries about your teeth then its best to consult a dentist as they'll be able to look at them and advise the ebst things to do,
you might want to think about switching toothpaste to that sensodyne stuff as it might make your teeth hurt less.