Need advice: head telling me one thing and gut saying another

A few days ago my hubbies mobile rang and it was our son so I answered it, as his dad was busy. After the call ended his apps where still open and his gallery app wa the first on screen. What I saw was rather startling. He had photos of himself wearing woman’s tights and loads of photos he had taken from the internet of random naked woman. He even had a video of him masterbating. I was totally flabbergasted and flew off the handle at him. His reasoning for it was he had supposedly taken the pictures of himself to send to me then decided it wasn’t a good idea and forgot to delete them (they had been on there 2 months) the pictures of the woman was it’s something to look at (he works away a lot). My head is saying just believe him but my gut is telling me those pictures were not for me and the pictures of the woman were sent to him. We have been married a long time and this is really upsetting me atm. Any advice please