Can hcg in blood drop quickly to less than 0.1 after a possible miscarriage 36hrs before test? dont know if was preg before that blood test or prev hcg level,had tummy bump+small blood,no pain,may have only conceived between 5days and 4 weeks at most

Impossible to say: It is possible for HCG to drop to less than 1 after miscarriage if the levels weren't very high yet in the pregnancy. BUT typically by almost 6 weeks the hcg would be high enough that it would take a week or so to drop. Unfortunately it is also impossible at this point to tell you if you were pregnant. I will say a tummy bump from pregnancy is highly unlikely at 5 weeks pregnant.