Why is this happening?

Yesterday i got this headache and i suppose it feels like pressure being applied to the inside of the left side of my head. Along with the headaches i feel nauseous. It’s extremely painful, it hurts when i move, talk, even move my eyes to look at something. Today i have the headache on the right side of my head; it feels the same as it did yesterday. I don’t usually drink a lot (of water and everything else) but i haven’t started drinking more or less than i usually do, so i don’t think that causes my headaches. I do sleep with a fan partially blowing on me, but again i do that every night so i don’t see how that could cause the headaches. My pillow isn’t the softest thing in the world; it’s kind of a couch pillow. I’ve been sleeping on the couch for the past month because i have a futon as a bed. But i just use one of the couch pillows as a pillow because my little sister keeps taking my regular pillow. I just don’t know what could possibly be causing the headaches and i really want to fix it so they don’t come back. Oh and i hate taking medicine, i avoid it at ALL possible costs. But yesterday the headache was so bad i could close my eyes or talk or anything without this horrible pain so i took an Excedrin, extra strength (we didn’t have Advil) and that seemed to help but at night my headache returned again. I really just want to figure out the reason why I’m getting these headaches and fix them. Please help, if you have any idea of what it could be just say it please. Thanks so much in advance!