Well, first I would try talking to your boyfriend about it. Tell him how you feel, and ask him how he feels, etc. Having a conversation about it is probably the best way to deal with it.
However, there is nothing wrong with watching porn. Many people do it, and it isn’t a problem unless it interferes with daily life because he is watching it so often (in which case it wold be an addiction). Just because your partner watches it does not mean there is anything wrong with your relationship, your sex life, or their satisfaction with either.