Fainted after blood test, NEED HELP PLEASE?

Last week i had a blood test and it said I had low potassium levels. I have since found out more about this and I think it is hypokalemia (hypokalaemia). It said I had to go back for another blood test to see how bad it was. My symptoms were excessively sweaty palms, hair loss, irregular periods and constant exhaustion. (we thought it would be my thyroid gland but it wasnt). I had another blood test this morning and felt fine after. then I went to school and was doing everything as normal, didnt feel faint or anything. then i was walking home (two hours after the blood test) and I fainted. I just felt a bit strange (lightheaded, dizzy) then the next thing I knew I was getting up from the floor. I didnt hit my head or anything. I have never in my life fainted before. Blood tests have never effected me either. Do you think this is because of the blood test or is it a symptom of Hypokalemia? Or do all these symptoms add up to something else? Thanks in advance :) (I am a 16-year-old female in the uk)