HCG levels, worried!

So I got a faint positive yesterday and as luck would have it I had a doc appointment today but her urine test came back negative so she sent me for blood work. I just got the call that my HCG levels are elevated but low only 13.5 and she calls that the "grey area" I go back on Monday to have blood redrawn and make sure my levels are rising. Has anyone ever experienced this? Should I be happy or worried. I don't know what to think!