Is it obligatory to repeat the prayer if there is a yellow spot without an odor on the trousers after waking up, knowing that there is doubt whether it is urine or not, and knowing that drops of water are discharged after urinating and washing that do not stop, and it might be water and not urine?

If you are not certain that a spot you found on your garment is impure, then the garment is not ruled impure, for the fundamental principle regarding things is purity. Nothing is ruled impure merely based on doubt. Your prayer is valid as long as you are not certain that the spot is impure, or certain that it is from semen from which you have not performed ghusl (definition). And if you prayed unaware of the presence of impurity, and then learned of it, your prayer is valid according to the most preponderant opinion, and you are then required to purify the garment.