Marrying Outside of Family’s Religion

I have been in a 4-year relationship with a man who is of a different religion than myself. My parents are extremely conservative and do not approve of this relationship. (In my religion there is no conversion and we must marry within the religion.) They are constantly making me feel guilty and as if I am a bad daughter, since they have done so much for me and I am somewhat dependent on them. I am having a hard time reconciling the Law of Karma. Though I am happy, my parents are also affected by this choice and they are extremely hurt. All their guilt and disappointment is even making me second-guess my relationship with my boyfriend. Do you have any advice for me?