I walked briskly to the train and walked up the stairs all in less than ten minutes. At the top of the stairs my chest hurt, then my ears, my eyes started to loose focus so I leaned against the wall when my knees felt weak I tried to squat down and lost control of my legs. I don't think a lot of time passed- maybe a couple minutes. When I got on the train I sat down and realized I was sweating perfusly. I don't know what happened to me- I feel okay now. Should I go to a doctor or is it possible it was something simple like low blood sugar?