Dear Alice, you must be going thru a very bad time now. All i can say is:

1) Let him settle it by himself as he wished but tell him to be true to you. No hanky panky as a r/ship needs honesty
2) Everyone deserves a chance and so does your bf and also give ur r/ship a chance as well
3) That girl's a real B*tch!!! Pure B*tch
4) Finally, I believe that you love him dearly to let him go now. So give the r/ship another chance but this time, be prepared. If anything happen, at least you wont be that hurt and finally realised that this guy is not worth your love after all.

Cheer up. okay

way to go... give it a chance before letting go something. This might strengthen the bond btw u both instead. for a better r/ship. good luck and be happy.