Help! my bf was looking at his exes profile page...?

i was on his cmoputer and when i went to type something in a list came down of history beginng with that letter and i noticed my bf ex girlfriend name so i went to his history turns out his past 2 exes one more 2 years ago and one he was hooking up iwth couple months before we got serious..... i dont know hwy he would do this i confronted him adn he was honest and said he did and it was once and he was just curious as to what they were up tonow and that he was off as quick he was on. and he assured me loved me and would never do it agian. i know theyre not in contact i just dont know why he would :( is it normal to just be curious? we have been dating 3 years