If yawning was not a sign of being sleepy or drowsy, why do i feel sleepy?

Question

when i yawn i feel sleepy but i learn that yawn is not a sign of sleepy or drowsy and its a deep, long breath cause of shortage of oxygen, but when i yawn i feel sleepy and my eyes have tears. why??

Answer 1

When you sleep, your body uses less oxygen. Perhaps you feel sleepy because you aren't breathing deep enough.

Answer 2

Yawing is a sign you are not getting enough oxygen at that time.  If you are not getting enough oxygen you are depriving your body so your body starts slowing down to use the oxygen it is receiving and/or has stored.  Hope this helps.