I'm upset that my boyfriend wanted to stay at a mates
What was his reason behind it?
I think he's cheating on me behind my back, and he's "staying at his mate's" place to use as an excuse to meet up with other girls.
It is important to allow your partner to have time with friends. If you feel uncomfortable about the situation then it may be a good idea to talk to your partner about it. Time apart allows the heart to grow.
But he's just going to go bang some other girl.
You have no proof he's cheating on you. Forcing him to not see his friends because of your insecurity isn't fair to him. If you are that worried, talk to him.