Do adult web site pop ups appear in computer history??!!

My husband and I most of the time are wonderful and a happy couple. We have sex often and everything seemed to be okay until I found his porn stash. Everyday porn searches and stained shirts everywhere (earlier in our relationship). He claimed that when him and I got together, he stopped with the porn. Now I have recently found porn searches on his cumpiter history but he claims they are pop ups but the computer has 3 different specific searches from porn stars he used to look up. I don't know if I should believe him when he says they pop up while he plays music while he's online playing video games. This hurts me deeply and need some advice on the outside looking in.