I Am Dizzy Alot

So Scared!... Hello, so the dizziness all started one Sunday in June. I was feeling really faint and I had just eaten, then I went to lay down and when I got up I didn't feel any better. I had been sleep for 4 hrs. which is NOT like me so my mom called the doctors. She dismissed it as nothing. SOOO now for 3 months I have been on meds and it still doesn't help and I still get dizzy. Now that it is September today I was just in class and when I got up to hand a paper in I felt extremely dizzy and then my heart rate got fast, I squated down on a wall, and the next thing you know I passed out. I really need help guys! Any advice?? It is really hard to live like this and I am getting weaker and weaker everyday. Got any tips??? Please any little bit could help!!

So far I have had an MRI, CT Scan and EEG and all came back normal.