You ask us, "Why does porn hurt me so much?" Really, you're the only one who can answer this question. You seem to have a bad history with porn that you refer to. Was it the porn, or was it the "bad man" who hurt you? Was your boyfriend hurting you in some way before you discovered the porn in his life?
Porn Is Not Bad If It Doesn't Hurt Anyone
Speaking as a man with a vivid imagination, I have to say that I've indulged in my share of porn-related fantasy. In truth, I think that women have a lot to object to.
Porn depicts women (generally) as sex objects, desperate for sex, and not much else, from the men (any man it seems) around them. Women are shown as victims of very degrading fantasies, sometimes violent, rarely as equals. They are the objects to be acted upon.
That being said, I think that if it doesn't hurt anyone really, it's not that bad. I think that there is a lot of stuff out there that is less offensive, that may, in fact, be therapeutic for people.
Porn Is the Symptom, Not the Problem
You clearly have been in some bad situations with men. Porn, in these cases, it seems to me was a symptom, not a cause of the problems at hand.
In the case with your current boyfriend, I worry that he is saying it is "your problem" rather than recognizing that you have real feelings that are brought up by exposure to porn. He's a fool if he thinks that something is "wrong" with your negative reactions. And, he certainly should be willing to not indulge in porn stuff anywhere near you.
Fantasy is part of our make-up
On the other hand, if he gets excited by porn, when he's nowhere near you, if it's just his thing, why does that hurt you? I think it's bad for relationships when one of the partners tries to control the others' fantasies. Just because he's fantasizing, doesn't mean he doesn't love you and find you desirable.
Fantasy is part of our make-up. Indeed, you calling yourself Princess is part of your own fantasy...isn't it?