We had an protected intercourse on 25th august and on 6th september i had my periods with back pain was only for 2 days bleeding( normaly it happen 4 to 5 days to me).then today is 5th october and no periods till yet am i pregnant ? Is it a implantation bleeding or what ?.i have done beta hcg test twice in a month one is on 1 october also both tests are negative showing hcg level less than 1.20 then is there any chances of pregnancy?.why i did not get periods till yet is there anything to worry about?