Naked pictures

Was Looking at boyfriends iPad and came across a couple of naked pictures of his parts..My first thought was "oh wow was he going to send them to me and then got too embarrassed"? We had never sent anything like that to each other before so I was surprised.  Shortly after I saw them I took a semi sexy pic Of myself to see if he would end up sending one or mentioning it, but nothing so I let it go, that wasn't really my thing anyway.  I forgot about this incident until a couple of weeks later I saw there were a couple more pics on the iPad.. None of which were ever sent to me! Totally knife in my heart feeling and sick to my stomach! Is he sending them too someone else? Why would this be happening more than once? Lost hurt and confused not sure what to think about this, he is very loyal to me and if would never cross my mind he would ever cheat.  Is it cheating if he did send a pic to Someone else? :(