What should one do if he feels drops of urine coming out during or after or before prayer? And is he obligated to stop the prayer immediately or complete it?

Whoever doubts that something has exited him during prayer should not leave until he hears a sound or smells an odor. Things are judged to remain in their original state until the contrary is certain, and an incidental doubt does not harm. So, whoever is certain of purity and doubts impurity is judged to remain in purity. There is no need to repeat prayers in which one doubts the annulment of purity.