2 missed periods help!!

Hello,

I am 16 years old and started my period this year in February.

On the 12th of august i had unprotected sex with my boyfriend in the heat of the moment. 17 days after I had tinny red spotting with lots of clots.

Its now September and I havent had my period for 2 months. Im currently overseas in japan and have been overseas since august 26th.

Im so stressed that im pregnant.

I have taken 2 pregnancy tests and they have both been negative. One was 14 days after having sex. And the other was a week ago.

Im not sure what to do...