Hello, I am 13 and often times after I stand up when I am at my house I see black spots and I get a bit dizzy. I normally feel this after sitting down for to long. If I stand up and it's really bad then I would stumble a bit and I would not really know what I'm doing as in I'm not really aware of my surroundings (can't hear that well, hardly can see things even though my eyes are open). Some times it's really bad but before I know it I am already on the ground and my body hurts but it's like I'm shocked and can't move for a bit but I still see the black spots. Should I be concerned about this?