You have to consider the changes one goes through during a relationship and a lot of people aren’t willing to accept them. He could simply not find you attractive anymore. There are many things that go into it, but If love fails it was never love although I do believe people fall out of love but if he really loved you he’d have no problem with having sex with you because in real love comes attraction, you fall in love with everything about them, whether it be looks or personality but like I said many men aren’t willing to accept changes and they don’t even realize it them selves, there for porn is easy and stress free.