Missed period

My period came the 16th of October . I had sex on the 31st of October. Had sex again the 9th/10th of November & had what appeared to be implantation bleeding on November 11th. Period still hasn’t come. Took a test Nov 23 and it was negative , took 3 on Nov 25 and all three came back positive . When is it likely this happened , Halloween or in November?