Is it obligatory to doubt the purity of the marital bed after intercourse if the bedding was not changed, especially if the bedding is dark in color and has lint that might conceal traces?

Cast aside doubts and whispers [of Shaytan], for the default state of things is purity. So, unless you are absolutely certain, with definitive conviction, of the presence of impurity on the bedding, then base your judgment on the principle of purity. And even if the bedding were to be impure, impurity does not transfer from it to anything it touches if it is dry and the touched objects are also dry. Therefore, sit on the bedding and pray on the prayer mat without any reservation.