Porn & Masturbating

I never ever saw a problem with my boyfriend watching porn and getting off to it until the other day he told me he was going to "jerk off" and I was jokingly saying "nooo wait till you come over" and he was like "why you don't like me finishing off to another woman?" that really made me like grossed out and not happy for some reason and now I'm kinda pissed lol.. is it normal for me to feel this way now?