my guy and porn on internet

dear sir, My boy friend is int porn and one day when i was on the computer i pushed history and sure enough he was on all kinds of porn sites. It shocked me because some of these sites were girls of ages 18 young ones. when i asked him he denied that he was on those web sites,it really hurt me that he lied and i feel betrayed, he buys magazines of naked woman too. I don't like this one bit but now that he knows I noticed he isnt't on the computer looking at web sites I think he knows how to erases them off the history part of the computer. Why do men get into porn is this normal behavior?

Yes, this is normal and common, but it is usually not at all appreciated by wifes and girlfriends.