Low hcg levels

Frankie
Hello!
Please can someone give me some reassurance?
Last period 1/10/16
Conception 27/10/16
Been having symptoms the last 10 days (cramps,constipation,etc)
I tested every day last week and all negative. 
Went to docs for blood test on Monday and they came back "raised but not quite high enough to confirm pregnancy"...or words very similar. 
I did a stick test last night and it came out positive. 
Is it possible my levels are just lower than average,or took longer to start showing?
I'm worried...
Thanks 
Frankie