Psychologically I think you can get hooked on anything pleasurable: food, booze, gambling and of course sex.
I don't think it's a physical addiction, though. You're not going to go through withdrawal symptoms if you abstain.
How to tell if you actually have a problem with it: if you are cancelling plans to hang out with friends in order to
look at porn or see SP's, that's a bad sign.
Sex should be a great part of your life, but only a part of it. I think people get in trouble with addiction when they have
nothing else going on in their life, so make sure you make time for friends, family, hobbies, learning new stuff, etc. Have a
well rounded life that includes enjoyable sex.