If the sensitivity is getting worse over time, it is a good idea to have a dentist check it out.
Sometimes, you can just be a little too hard on your teeth. Try changing toothpaste brands and avoid whitening options, as they can weaken the enamel on your teeth causing them to become sensitive. You may even be brushing your teeth too hard, so try brushing more gently or using a toothbrush with softer bristles.