Thank you for sharing your question with the EmpowHER community.
Since you took a plan b on the 25th two days after having unprotected sex, it's more than likely the spotting is from the emergency contraceptive pill. If your menstrual cycle was starting to be some what irregular, the hormones in the emergency contraception will only increase or prolong it's irregularity.
It's going to take time before your hormones balance out. In the meantime, don't introduced another emergency contraception (more hormones)to your systems. It will only make things more irregular and is not good practice anyway.
I hope this helps.