You can pick up a pulse oximeter that has a recording feature. This comes with software that allows you to download the data to your computer.
If you do a lot of research, you can find some of the fundamentals of how to interpret the patterns, and this will give you a rough idea of where you stand.
An example of a recording pulse oximeter can be found at http://www.clinicalguard.com
and one model is the CMS 50 E.
Another option is to just have someone watch you sleep...