Nasal obstruction has been shown to be associated with obstructive sleep apnea. When the obstruction is complete it can cause a reduction in blood oxygen levels, especially in obese individuals.
But, the first order of business should be to determine the cause of the nasal obstruction and relieve it. The 2 most common causes in adolescents and adults are deviation of the nasal septum and nasal polyps, the latter often associated with chronic allergic inflammation of the nose. A deviated nasal septum can be corrected with surgery. Nasal polyps were, in the past, often treated surgically but at this time treatment with an inhaled nasal steroid, such as FlonaseĀ® (fluticasone), can effectively shrink the nasal polyps.
You should make arrangements to be seen by an ENT specialist. What you have is a treatable problem and should be treated so that you can breathe through your nose all the time.
Good luck.
well, is your question "why is it hard to breathe through my nose"? id think logically it takes longer to get sufficient oxygen through narrower tubes, such as your nose. and youd probably know if you had sleep apnea or not. look that up dude