Welcome to HCM
I can understand your anxiety
,but it is possible to become pregnant because even pre ejaculatory secretion may contain sperms,although chances are less.
Please do not be too anxious and wait for some more time and get a pregnancy
test if it is negative and you get a normal period then there should not be any problem.,but positive you can consult a Gynecologist she will guide you to correct way to deal with such problem.
A false posive test is not common but if any kind of doubt is there you Gynecologist may get blood test
for Beta HCG
. If that is negative surely you are not pregnant.
But at this tender age you should pay attention to your studies,I am happy that you realised that it was silly.
Just take care.
Best of Luck.