Advice an help

Lexi

Me an my boyfriend have been together for 4 years me and him broken up 2 summers ago an during the break up I dated his best friend ( Ik shittt) but I just found out last week that him an my best friends hooked up an both felt shitty afterwards an kept it from me for so long an we’d all hangout an shit still an like idk what to do he’s my first love shouknt if asked her to do it but he was coming from a hurt spot from me but for my best friend to say yes is what’s really getting to me like what should I do I’m so broken rn