Is ghusl or ritual purity required, and is prayer acceptable after experiencing pain in the urinary tract, pressure on the private parts during sleep with the possibility of fluid discharge, then holding urine, and noticing a viscous yellowish-white substance before urinating?

If you suspect something has exited, the default is that it has not, until certainty to the contrary is achieved. The white substance that often appears is usually vaginal discharge, which is pure and nullifies ablution, but does not necessitate a ritual bath (ghusl (definition)). If you are unsure whether the discharge is from you or something else, choose and assign it one ruling from among what you are doubtful about. If you are unsure about the time of the discharge, it should be attributed to the closest possible time it could have exited. So, if it is possible that the discharge exited after the prayer or before it, it is ruled to have exited after the prayer, and the prayer is valid. Beware of obsessive thoughts and indulging in them.