A: I would say he's either cheating or just isn't attracted to you anymore. Unless you're long distance, no guy would want to be away from his girlfriend for three weeks. And if he was, he'd want to have sex immediately.
A: Some guys have a problem doing this because they think it's disrespectful to women. Especially younger guys. You really have to let him know that it's okay for him to initiate and lead the action and that you'll let him know if you're uncomfortable.
A: I have to disagree a little with sexwiseman. Maybe it's because I have sensitive skin, but leaving soap on unrinsed can hurt after a while. The travel deodorant in your purse is probably your best bet.
A: Nipples can get erect, but that's about it. And it doesn't necessarily happen all the time, like it would with a penis. Mine seem to respond more to temperature than stimulation.