Episode Of Passing Out, Had Chest Pain, Blurred Vision, Slurred Speech, Irregular ECG, Blood Flow. Have Continuous Headache Since. Cause?

Hi, I am a 16 year old, healthy girl. Ive never had any extreme medical problems until just recently out of the blue. I passed out in school, for no reason at all. When i came back to my senses like approximately 5 minutes later, my chest was hurting really bad and i couldnt see clearly nor could i talk clearly. My speech was slurred. It felt like a ton of bricks had been placed on my chest and they were just left there. I was rushed to the hospital and they ran all kinds of tests on me. My EKG came back irregular and my blood flow was irregular. It was really hot but i my body was freezing cold . They sent me home like 2 hours later. Everything was fine except for the horrible headache that i had. It was only on the right side of my head though. Now, almost a month later, i still have the same bad headache on the right side of my head. I get really dizzy sometimes and my chest tightens up all the time and it gets really hard to breathe. Its like excrutiating pain in my chest when it tightens up. What can this be? What can the cause be? Is there anything i can do to get rid of this and to prevent it?