Today when i stand after sitting I get very dizzy, I shake and I start to black out. I even tried to hold onto a wall one of the time but the shaking caused me to hit my head. I noticed that my heart is beating fast after it ends and I return back to normal (it usually lasts around 10 seconds). This happened about6 times today. I am a 16 year old girl and I am taking stressful classes in school causing me to be stressed and lack sleep. I am on Adderall for ADHD but that is nothing new. My jaw also started twitching (similar to shivering) this morning.
What is going on with me? Is it a serious problem? Is my brain just exhausted?