This guy I like hangs with his best friend which is a girl he told me he doesn't like her but they spend so much time together I'm really jealous

An advice:
Life is too short to get jealous all the time, stay away from drama, do your work.
Be light hearted about love.
If it's yours, then it will come to you.
The more you think about others, the less you take care of yourself.
What u going to do with him then? He already said he didn't like her.( he might be lying) but he is clear about it, and if u want to heat his honest answer that night hurt u more. Why let others hurt you?
Let it go...

Being jealous will get you no where.

Being happy and nice to this guy will.

If he says she is only his friend then why don't you ask him out or something? It can't hurt.