Yes in fact I have it right now haha, been on the laptop too long. If you mean the sort that covers your outer ear, because the pressure of the earphones pins your ears in a way that is not natural and over time they become agitated. If it is the ones that go inside your ear though the same thing can apply. You have a concentrated source of sound and a constant strain on the natural setting of your ear. You have something sitting in your ear so it also agitates the ear. It will pass but I wouldn't make a habit of keeping them in as long as you probably know by now :D
Yes, especially if the weather is warm and your body is sweating. Its just your body reacting for a foreign object irritating the area - this happens alot with ear buds that go into the ear.