Weirdly stressed

I don’t know why or how, but I feel stressed. I have felt stress for a while, I always brush it off because I believe that I have no reason to be stressed. I sometimes feel smashing my head into a wall, pole, table, door, and the ground, I don’t get why I do. All I long for is to be away, alone at the park, in an empty world. Recently (not anymore), I didn’t feel like eating.