Even if I yawn, tears don't come out from my eyes. What can I put in to lubricate my eyes?

Artificial tears. It sounds like you are suffering from dry eyes. This is a condition caused by a decrease or imbalance in the amount/type of tears that you produce. The mainstay of treatment is lubricating eye drops (artificial tears), but there are other available options that may work better. If artificial tears do not help within a week or two, see an eye doctor to evaluate the exact cause.