those who got a bfp on a skipped period

Ka
I skipped a period for some reason suppose to get it on06/16. And got a positive opk on 06/05 before the missed period and on 07/02 after the missed period. I got a faint positive today at 8dpo how do I know when my due date is? I won't be able to get in the doctor right away for just asking if anyone has experience with this or knows