I need ideas on how to find out my husband is cheating

Hi ladies . I’m wondering in what ways can I get solid evidence that my husband is cheating. I suspect he is cheating because he stopped all of his “husband duties” , even sex and I found pictures in his phone of this female alone and pictures of them two together . He deletes messages so I can’t get solid proof there . His phone is a dead end . So what can I do ? Please help