Can a qualitative hcg serum blood test be incorrect? it says that no hcg was detected or less than 1. can it be incorrect and can i possibly be preg?

Possible: If you test too early the test may be negative; the test only measures what is present in the blood, if you test too early, you could be pregnant but HCG level has not reached above the 5 units that is the cut off level for diagnosis of pregnancy. See this site for info on this topic. http://www.webmd.com/baby/guide/pregnancy-am-i-pregnant.