Could a blood test come back neg 10 days after sex:(???? HELPPP?

had a blood test done 10 days after sex. It came back neg :(...Is it to soon for a blood test.....When should I take a another test? I sware I had implantiton bleeding or am I WORNG????? I dont know when my next period is going to be becuase I dont have reg periods???So how many days after sex are you sup to wait...TODAY IS DAY 14TH...SOO UPSET