Is the water with which I washed my private parts, and the water that was on my underwear and reached my trousers, considered impure? And have the things I touched in the house become impure? And have the entire house and its occupants become impure? And what should I do?

Obsessive thoughts have reached a great extent, and the cure for them is to completely ignore and disregard them. The default state of things is purity. Therefore, the water that was in the underwear is considered pure until its impurity is proven. Consequently, neither the pants nor other clothes become impure, nor do clothes or items in the house touched by hand become impure.