This seems like an issue between you and your girlfriend. If she is worried about you cheating, you should ask her why. Perhaps she is insecure and needs you to tell her that you would not cheat on her.
Yes
It all depends on trust, if she really loves you then she has no need of cheating on you with other friends. It all depends on trust, if she really loves you then she has no need of cheating on you with other friends.
Cheating
Yes, its that simple if your with some one else at the same time that your in a relationship,your cheating theres no way around it....(friends with benefits) call them what you want cheating is cheating.
Yes you should tell her that he is cheating. Because later, it will hurt her if not told.
Of couse it is; that's just wrong and cold. Cheating is by definiton having sex with someone who is not your partner.
Do you mean like cheating on someone or trying to hide it from friends and family?
talk to her and try to work it out
Your friend's hot girlfriend. (Ba-dump ching!) I suppose it depends on how good a friend he is, and exactly what you mean by "looking at you."
If your friends laugh at you and your girlfriend then don't pay any attention to them, and stick up for your girlfriend. That will make your relationship go farther. And you can also know that if they make fun of you, then there not true friends.
if there your real friends then they would be supportive of your relationship, and you shouldn't let your friends make fun of you girlfriend. remind them who has the girlfriend around here, And maybe they should get a girlfriend. But if you tell them to stop and they won't then forget them.
What I would do is tell him that she is cheating and give him some good proof and if he dosent want to believe you then that's his choice. Hey! You warned him!