A: Really boxers are hot, boxer briefs hot too. Usually, briefs are for your grandfather. They really in no way, turn a girl on. Stick to the other two.
A: Well, it seems you girlfriend is jealous. You need to build up her trust by showing her you care for her, and are interested in her only. Also, make sure to keep any flirting or overly friendly behavior to a minimun especially when your girlfriend is around. But don't ditch or lose a friend over... more