Are over-the-counter inhalers good for you or should you get a prescription?

In general not good. In general otc inhalers are not great. Like otc nasal sprays that can cause rebound and problems if used for more than a few days in a row. If you need something to help you breath you need to see a doctor.
Prescription. If you are having difficulty breathing on a regular basis, i would definitely get this checked out by a doctor, get a diagnosis, and get a prescription.