What is the ruling on wearing ordinary (non-undergarment) clothes that have not been touched by semen or impurity, if they were worn over undergarments that had been touched by semen at the time of ritual impurity (janabah), and then worn again after purification from janabah?

Semen is pure. It is permissible to wear outer clothes over inner clothes that have become impure. A person does not incur sin by doing so, but it is necessary for him to purify the defilement for prayer or to remove the defiled garments. Dry impurity does not transfer to dry clothes. Doubt about the transfer of impurity is not taken into consideration. If you are afflicted with obsessive whispers (waswas), it is best not to do anything that would increase them. The cure for such whispers is to ignore them and pay no attention to them.