“Why does it hurt to wear my retainer?”

If you are wearing your retainer for the first time shortly after completing orthodontic treatment, any discomfort will resolve very quickly. If you are wearing your retainer and the retainer was made quite some time ago after finishing orthodontic treatment, there is a chance that your teeth have moved. I suggest you return to your orthodontist for an evaluation.

Russell A. Sassack, D.D.S.

Retainers can have a variety of designs, and without seeing yours, I cannot know what type you have. However, I can say that the most common cause for retainer discomfort is that the teeth have moved when the retainer is out of the mouth. These are concerns best answered by your orthodontist. 

Pressure on teeth from the retainer can cause discomfort.
Regards,
Dr Manson