My age is 20 my period date was 11 november to 16 november I had sex on 23 november sex means only rub private parts then my period delayed for 4 days then they came only 3 days after that I took at least 8-9 pregnancy home test till 31 december all came negative after that I took first beta hcg serum test on 31 result came 18 after that I took another test on 5 jan result came 0.90 after that I had my period on 15 jan but they stayed only 2 days then I took another beta hcg result came 0.20 what is that mean? Why my periods have shorter then usual please help.