This is serious i need help!?

Ok this might be long so read on please. I had hit my head really hard on a metal wall and it started to gush blood and i soaked it up in my sweatshirt and never told my gym teacher. When i got home my mom washed it and checked my head she said to put some ice on it because there was a little bump. Now im all better with that but since then whenever i sit down kinda low like on the floor or the couch and i get up my head gets all these colors and i can't see for like a few seconds and everything is blurry with different colors. I have told my mom and said it was nothing. But it has been happening ever since then. What is it i really need to know and no i can't just go to the doctors in personal reasons. I am really scared though and i need someones help. please help me! I am 11 years old and a girl.