Help abusive relationship?

I have problem with my sister husband. He started about a while back to bring his friend over when he visit to start acting funny with me. Because he is my sister husband I felt I could not refuse it and now it has turn to ual acts of an improper nature. Although had never occurred he has shot his sperm on my face, placed objects in my and made to drink his urine. How do I stop before things go farther. Thanks.