Help : I need to stop looking at internet porn .?

Every now and then I look at porn but every time I get on computer i don't look at porn. I can go stretches without looking at porn but some days i can't resist the temptation to look at it. Same thing with masturbation. Sometimes I masturbate without porn, sometimes I masturbate by using my imagination or looking at a sexy magazine. Do i have a sex addiction or porn addiction or is something else going on ? Is this normal for a guy. Do all guys go through this struggle ?