Is my prayer valid with the presence of profuse, clear, watery discharge after menstruation, which necessitates changing undergarments?

These clear, watery discharges are fluids that exit the womb to cleanse it, and they are an indicator of a healthy reproductive system. They are pure and do not need to be washed, but they do invalidate ablution (Wudu') according to the majority of scholars. If they are continuous, you perform Wudu' when the time for prayer begins, and their subsequent emission does not matter. If they are intermittent, you wait for them to stop before praying, provided that this does not cause hardship.