my bf secretly dating my best friend

they dated for a long time without my knowledge, i just found out today, my best friend who dates my bf, told me. idk if theyre dating or no but they once went dating only two of them. not once but twice, not twice . i dont know how much. she only told me the newest. They even touching. they giggling, they.. it was so hurtful. it hurts to hear .it hurts to type. im so disappointed. he manipulated me, he lied to me, Even my OWN CLOSE FRIEnd lied to me. im glad she confessed everything today. disgusting