Is my prayer valid if I suspected a drop of urine came out after Fajr prayer, but saw nothing, then a drop came out by pressing the penis?

If a person performs ablution (Wudu') and then doubts its validity, the default assumption is that their purification is sound. This is based on the Prophet's (peace be upon him) saying: "He should not leave (his prayer) until he hears a sound or perceives a smell."

The questioner's prayer is valid because he did not discontinue it based on mere doubt. The excretion of urine after squeezing the penis does not affect the validity of the prayer and is not required for the completion of purity; rather, it is an innovation (bid'ah). Urine exits naturally, and once emptied, it ceases. Squeezing the penis can be harmful and opens the door to obsessive doubts (waswasah).