My Husband's Brother Seduced me into Anal.

My husband's brother started bribing me into sex because he recorded me the first time and figures he can use that against me. He showed up to do work for my husband and ended up, seducing me and letting him fuck me in the ass. This has to stop, but I just don't know if I want to. Honestly, I can't keep fucking my husband‘s brother. Ugh.