Hello dear
I understand your concern
First about pre ejaculatory fluid:
Pre ejaculatory fluid contain sufficient sperm concentration and it enter in to the vagina unknowingly before the ejaculation in the vagina.
So it can cause
pregnancy when sex was done in fertile phase of cycle.
But you had sex just 2 days after the period and it is safe period of cycle, so pregnancy is not possible in your case.
Bleeding after
plan B pill:
It is side effect of the plan B pill.
It contain high
progesterone and cause
breakthrough bleeding due to progesterone withdrawal effect.
So it common and occur in 50% cases of Plan B user
There is no relation between weight and its action.
So in your case, chance of pregnancy is nil as you had sex in safe period and you took plan B pill.
Plan B pill also cause earlier/delay in period.
Just avoid
stress, take healthy diet, drink plenty of water and do regular exercise.
Use safe sex practice in future to avoid unwanted pregnancy.
Hope this may help you
Contact HCM for further health query
Best regards
Dr. Sagar