Very low level of HCG - worried!

A
I'm 5 weeks pregnant (but in reality 3w) and my first blood work at 2 weeks after conception was 41 and yesterday I had another blood test which was only 300 UI HCG... I should receive a call this afternoon with my doc so that she can explain me this, but until now I feel so worried that something is going wrong, I feel so sad... Yet happened to one of you?