The cause of this fear has a lot to do with childhood experiences. It may take some counseling to be able to overcome this because it can be very painful, for you and for those who love you. Sexuality is a part of life and God created men and women to be mates and his purpose was for them to fill the earth. Sex was not meant to be dirty like what's found in porn. Also, he is against acts such as rape and child abuse.
I find that prayer and meditating on God's word has helped me through different trials and traumas in life. Besides counseling, try praying about it. Never underestimate the power of prayer. Philippians 4:6,7 says "Do not be anxious over anything,but in everything by prayer and supplication along with thanksgiving, let your petitions be made known to God; and the peace of God that surpasses all understanding will guard your hearts and your mental powers by means of Christ Jesus."