I agree with quiziccle.

There are all sorts of possibilities which often cause a difficult time focusing. All 3 diagnoses may cause this tendency. Are you being treated medically for your medical illness? Were these symptoms there before your treatment began? Is the difficulty becoming worse as times passes?

If these symptoms are creating a lot of trouble in your life (relationships, job, school, etc) than I'd certainly recommend talking with your doctor about it ASAP. Hopefully, some adjustments to your meds will relieve those symptoms, so you are able to actively participate in your life.

Best wishes to you!