Hi, I Have A Quick Question. I Went Into The

Hi, i have a quick question. I went into the doctors on Friday due to not getting my period. My last menstrual cycle was on the 2nd of August. My pee test came out negative but i was told to go back in for a blood test but wait another week. I started taking folic acid vitamins that the nurse said would be good and now my period came? Could you explain to me what it could be? I'm so confused.