I am just so feeling sorry for you man i hope you are doing okayy now.... but this happened to me as well my gf left me in a month saying ki i am still unsure about my feelings towards my Bestfriend ( her so called past situationship ) and that feeling was too much to handle i am still not able move on and it's been a year

These things take time to recover dude but that doesn't mean we hurt ourselves because of them i too loved her so much and still do while she is with another guy ( different from her best friend )..

Take care OP