Christian dad completely against masturbation, HELP!?

I have been completely secret about my "private" life for 17 years now, a few days ago though at 11:00 at night my dad stepped in on me unexpectedly and saw everything before I had a chance to switch browsers. He then sat down on my bed and said "life can can be tough" and promptly left my room. After this I googled similar experiences and found that in almost every case the parent had been ok with it mostly because they had had "similar experiences". This was a relief to me. The next day however I was indubitably mistaken and unprepared for what was about to happen. He pulled me over at a random time in the day, looked me DIRECTLY in the eyes and asked me "are you ever going to visit those dirty sites again?" I froze. All of the advice I had received online had completely backfired. out of desperation and fear(of getting my computer taken away or worse) I quickly answered no as naturally as possible. he then replied good and let me on my way. My dad is the closest to a true fundamentalist christian I have every seen with my two eyes and is stubborn, stubborn, STUBBORN. not only this but both my mom and my dad are against any type of or masturbation, and most types of birth control. I am not allowed to have locks on my door and my parents have a rule where they are allowed to walk in on me whenever they feel like. Again they are stubborn and I can rarely convince them to change their minds on anything. Is my best option just to lie and hope to not get caught again? any comments are welcome.