Your spotting about a week after taking the emergency contraceptive pill is most likely a withdrawal bleed from the hormone dose, not implantation. You're too early for implantation bleeding, which usually shows up about a week after ovulation. The timing you're describing fits the pill reaction better. Light pink-brown spotting with no heavy flow is a well known reaction to this kind of pill.
Next Steps
A home
pregnancy test after your next expected period will tell you for sure there's no pregnancy. Your period may arrive a few days early or late this cycle because of the pill, so keep track of the date.
Health Tips
Please see a gynaecologist if your bleeding becomes heavy, your pain gets worse, or your period doesn't start within a week of when it's due.