Do I have the right CPAP mask size? I have to strap it on so tight to obtain a seal that it hurts.

It's important not to over-tighten your mask. Doing so may be a sign that you have the wrong cushion size or an incorrectly adjusted forehead support. If you experience difficulties in fitting your mask, please refer to your mask user guide for complete fitting instructions or discuss this with one of the ResMed team, your local ResMed authorised dealer or your doctor.