Hi.
I can understand why it might be difficult for you to acknowledge that your boyfriend is turned on by watching other women's bodies--that can be a real anxiety producer--but remember that the women in porn are strangers, not anyone your boyfriend is going to go out and date. Also, the fact that your boyfriend likes looking at other women's bodies doesn't mean that he doesn't like your body or that he's looking for some other type of body.
Keep in mind many people enjoy pornography, both men and women, and not all for the same reason. For some, pornography is about an attraction to a type of fantasy or lifestyle (like bondage, for example), while others enjoy pornography because they are attracted to the actors or actresses. Either way, enjoying pornography is something that is common and normal. If you would like to learn more, you can check out these fast facts on pornography.
But back to the situation at hand: From what you've said, it sounds like your relationship is fulfilling otherwise, so it might be best to keep his porn-watching in perspective and to try deal with the feelings that come up as a result of your recent discovery. You might want to try talking to your boyfriend in a straight-forward manner if you want to know for sure how he regards porn. It may make you feel a little better about the situation.
Alternatively, you can explain to your boyfriend again, how his behavior makes you feel and ask him to stop watching, but he may regard this as overly controlling. Setting boundaries with him may be more appropriate. For example, if you don't want him watching porn around you or if you would like him to be more discreet about it by erasing the browsing history from his computer after viewing, tell him so.
You may regret giving up an otherwise great relationship. Plus, there is no guarantee that this issue won't come up again with a future boyfriend. Try to deal with your feelings now as much as you can.
Take care.