This is a difficult situation. But for a moment, let’s try to see it from their eyes. They have done their best to raise you the best way they know how. They have taught you what they believe to be right. They may now fear for your eternal well being. You should thank them for caring so much about you–whether they are right or wrong!
Now, as an adult with a family, you are not accountable for how your parents feel about your religious decisions; you are accountable for how you raise your family and model the love of Christ to them. If you have prayed and asked God to confirm that you are in the place He directed you to be, then you must press through all of the concerns of your family members, while being diligent to pray for them and respect them and their beliefs.
“And he answered and said unto them, Have ye not read, that he which made them at the beginning made them male and female, and said, For this cause shall a man leave father and mother, and shall cleave to his wife: and they twain shall be one flesh? Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder” (Matthew 19:4-6).