My short version... these 'headaches' are cause by using your mind to much... if you have the feeling that you are in your mind all day long, then you are are ovelorloading your brain with thoughts and worries.. and naturally that causus a headache.. a headache that you feel as is your brain is in in tight space or or robe is tight around your forehead with almost no space left so to speak. So like you say it's some sort of pressure, but it's not a real migraine, it's just that your mind is working overtime and that is normal for dp-ers. But it cannot fysically hurt your brain except that it makes your brain brain feel like it's burning or like it's being strained. But again no worries, it's normal for people with dp.