Confusion

opk, bbt, and cm comfirmed ovulation was oct 28-29th. AF is due nov 8th. According to Web md hct is not present till implantation on dpo8-10, hpt says it can detect 5 days befor af is due. I would only be dpo5. I am so confused.... dpo 8 would be the day befor af is due n dpo 10 would be af day#2..... can some one make sence why hpt say it can detect 5 days befor af is due to visit? And how soon I should get a bfp with out waiting for af?