I can understand your concern.
Well, according to studies ,if you take plan b pill within 72 hours after you've had unprotected sex, then it can reduce the risk of pregnancy by up to 89%. So, chances of pregnancy with correct use of plan b pill, are very very slim. You had unprotected sex on December 19 and have taken plan b pill on December 20, it was the correct time. You would not get pregnancy, from this incident.
Regarding sex on 23-24 December, as it was protected, so again chances of getting pregnancy from this incident is very very slim ,unless condom break off.
To be honest, i would not be worried for pregnancy.
Having light brown spotting and cramps could be due to side effect of plan b pill. It would become normal by next cycle. Yes, it is common with women to have imbalance of hormones due to plan b pill, and thereby bleeding time, may get changed. Don't worry, you are not pregnant.
I am sure, your cycle would turn back to normal by next month and you would get same regular periods.
Please don't worry, you are not pregnant, and your cycle would come back to normal by next month.
I hope this helps.
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