Stay away they are both trash to treat you this way to start with. You need new friends.
I don't think it's a bad thing, because of the fact the he broke up with you.
NO. theres always a reason for a break-up.
i think that you should tell your best friend that if she goes out with him that you will not be her friend
They are probably not a very good friend and you should seek friendship elsewhere.
If you and your boyfriend are still dating and have not split up then this friend of yours is not a true friend to you and you should consider her a toxic friend and walk away from her. If you and your boyfriend broke up and she dated him and obviously didn't tell you it is probably because she didn't want to hurt you. In this case talk with her and tell her that she should have been honest with you, but you should still remain friends.
He probably broke up with you because he was cheating on you with your friend. Then he showed up with your friend.
Since you broke up with your boyfriend it is highly likely that now that he is dating your best friend you are either jealous and it probably isn't love at all, but you just don't like to see him date your friend.
Get the friend to talk to him and if the friend won't slap the friend in the face
you should say nothing because there would not be any point.
Slap him
no he should not because i use to have a lot of boyfriends and i broke up with them because of that
If you love him of course you should try and ask him for a second chance. However be aware that he might not be very happy about you dating his best friend.