She took plan B a month ago

Hi, the boyfriend here. Ill try and give as many details as I can. On the 26th of August, one day after her period had ended, me and my girlfriend who are both 16 (legal age in Australia) engaged in a sexual act. There was no penetration but the slight chance of some pre-cum being on her hand that touched herself scared us a lot. She didnt believe she needed plan B as the chance was unlikely but I went to the pharmacy and bought some and asked her to take it which she did. She took the pill 18 hours after the potential conception.

On the morning of the 2nd of September she started bleeding. At first I researched and scared us that it couldve been implantation bleeding but I ended up concurring that it was withdrawal bleeding. This lasted for 4 days until the 6th and except for the first and last day was slightly stronger then her normal periods.

Due to her period starting somewhere between the 20th-22nd of August and the knowledge that plan B can push a period back normally around a week we said that her period should probably come before the 27th or 28th.
Its the 26th today and she hasnt had her period though she has been feeling very tired for around a week.
I keep scaring us by looking at the pregnancy timeline which says that exhaustion should set in around this time and keep thinking along the lines off “well shes been very tired so…”

Id really appreciate anything to settle her and my nerves. She hasnt taken a pregnancy test yet.