Bf cheated with best friend..

Lizzy

So I just found out that my boyfriend cheated on me with my best friend and this happen 3 months ago but he just told me and he says the reason he didn’t tell me sooner was bc she begged him not to tell and honestly I’m so confused and hurt like I have always been there for her for everything and I just idk anymore I’m so lost and hurt ughh..what hurts more is she started it.. just why..how could you do that to ur own best friend I don’t trust anyone anymore.. wtf is wrong with people...