If you still have feelings for him you can't do much but talk with your best friend. If she is a good friend then she will not began a relationship with him.
because he still fancies you
That's possible. But there's a chance that he's friend with her boyfriend. If he isn't his friend, there's a possibility that the boyfriend still has feelings for the ex girlfriend and is being nosey about her new relationship
This question is tricky... Does your best friend still have feelings for him? Would your best friend care? If you want to know the answer to this question, you need to ask her.
You could get someone to talk to like a best friend or find something to keep your mind off him
First of all you don't. If you do, she will never go for you.
are she and her boyfriend having troubles? maybe she's liked you before she got the boyfriend, and feelings are still there. ask her. if she's interested in you, she will tell you.
still likes you has feelings for you wants to be with you again
still has feelings for her
You still have feelings for your old boyfriend.
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.
It means that you still love or have feelings for him.