I am a healthy 28 year old.  I eat quite a bit of food in small amounts and sleep on average 7hrs/night.  My mom and grandpa both have severe diabetes.  I have a high chance of also getting it.  I don't know if that has anything to do with it.
When I stretch I throw my arms over my head and contort and stretch my entire body typically while unconsciously holding my breath.  I get very lightheaded and have to grab ahold of something sturdy and hope that my head doesn't come down on something hard.  I tend to lose my sense of hearing or at least don't pay attention to noise.  I am very aware of how lightheaded I am and how close I am to blacking out.  
My diet consists of little to no soda.  I drink 8 glasses (or close to) of water a day and eat a combination of peanuts and granola bars throughout the day.  When I get home I will eat a real meal and usually pretty late at night.
I also tend to get very light headed when I drink water at my desk.  I say my desk cause when im outdoors or lounging around the apartment I dont feel it.  
Does anyone have similar experiences and/or advise for me?