When do you accept your out?

15dpo (I believe - clear blue ovulation being rubbish this month, apparently I never had an LH surge, went straight to a solid smiley, no flashing), cd 31. Irregular periods since coming off BC (last 3 cycles 18 days, 14 days, 22 days). hpt bfn this morning. No period/pregnancy symptoms. When is enough enough and I accept it's not my month? Surely I am out now and it's just my daft cycles after the implant?