I cheated on my husband with his brother, help?

My husband and I have been married for two years, before that we were together for three years. We got into an argument about something so pointless, it was just so stupid and he ended up walking out to his brothers house and told me he hated me. I was upset and I went to his brothers house to speak to him and he wasnt there, but dale (Brother in law) took me in and we got chatting. I was really upset and somehow we kissed and managed tto sleep together. I knew it was wrong but idk what got over me. My husband came bk yesterday and told me he loved me and asked me to take him bk..what do I do?