Think of it like this, an IC is supposedly 10miu, if you start with a non pregnant level of 2 and your hcg doubles every 2 days and you implant on 7dpo on 9dpo your levels are 4 and on 11dpo your levels are 8, so still below the '10miu ic' on 13dpo your levels are 16 and you should show positive! Good luck x your not out till shows x