Girls, a question: I already have a child — with him I didn't even kno…

Girls, a question: I already have a child — with him I didn't even know I was pregnant because my periods were always irregular. Now my cycle's off again in June, there was no PMS, and the period-tracking calendar shows I'm pregnant. I had an hCG test last week and it showed 0>10 — what does that mean? Some say it's possible I'm pregnant, others say not. Each lab has different reference values; I'm going to have my blood retested tomorrow.