Hi Welcome to HEALTHCARE MAGIC..
I have gone through your query and can understand your concern.
No the brown vaginal spotting or bleeding you had should not be
implantation bleeding. It should be
breakthrough bleeding as per my opinion. Breakthrough bleeding occurs due to intake of
emergency contraceptive pill & normally occurs within 3 weeks of intake of pill & you should not be much concerned about it.
This occurs due to action of high dose of
levonorgestrel in emergency contraceptive pill which disrupts your normal menstrual cycle & causes this bleeding. Breakthrough bleeding means that intake of
plan B pill was successful in preventing
pregnancy by disrupting your menstrual cycle, hence bleeding occurred. This bleeding has not relation with getting pregnancy.
Chances of implantation happening following intake of emergency contraceptive pill intake is very less. Also ovulation to happen in cycle following intake of emergency contraceptive pill is very uncommon.
An emergency contraceptive pill is intended to use in case of emergency purposes. These pills can cause
irregular periods & other harmful effects. Use condom or regular contraceptive pill regularly as method of preventing unwanted pregnancy in future.
However as you had multiple sexual intercourse in past month, you are advised to rule-out possibility of pregnancy by doing a pregnancy test as well
Don't worry you would be fine
Hope this information helps