So the most likely solution to your sensitivity would be to
(1) Minimize acidic drinks, like soda, juice, and lemon water
(2) Start using a toothpaste for sensitivity, like Sensodyne or Colgate sensitive. Be patient with these - it may take 1-2 weeks before they really start working.
If the issue is still not resolved, your dentist may prescribe for you a stronger toothpaste, or, if you seem to be grinding your teeth too much, may make you a nightguard to protect your teeth from abrasion.
Note: There are endless treatment options for sensitivity. Try these first. No one should have to live their life avoiding a good ol' ice coffee!
1. Brush and floss every night before you go to sleep. (Morning helps too of course, but night is far more important). Don't have anything other than water after you brush at night. And make sure your toothpaste has flouride in it.
2. Minimize acidic drinks (soda, juice, lemon water), or if you can't, at least drink them with a straw, and/or rinsing with water afterwards wouldn't hurt either.
3. Avoid snacking between meals. Remember, it's not just table sugar that causes cavities - any food with calories will do the same if it's stuck on your tooth.
4. Remove your wisdom teeth, unless your dentist tells you otherwise.
5. If you're a grinder, get a nightguard.
What is too much? If you're using a mouthwash without alcohol, use as much as you want. The problem with alcohol is that (1) it tends to dry your mouth out over time and so could make thing worse, and (2) excessive daily alcohol exposure in your mouth comes with a very, very, slight increase in oral cancer.