Could I be pregnant?

I feel stupid writing this. Let me explain.

I’m fourteen, and 12 days ago me and my now ex had unprotected sex. He did not ejaculate inside of me; but before the sex happened he had came back from *getting himself off* and actual ejaculate was over his penis. We had sex whilst this was the case. I need to clarify when the sex stopped —- the ejaculate was gone from his genitals because it was inside me. Anyway, the sex didn’t last a significantly long time and afterwards everything seemed okay.

I got forced to take a pregnancy test by my residential placement a few days ago; 8 days after the sex had happened. It came back negative but I heard that pregnancy tests aren’t accurate that early on? Anyway, I’m not sure what to think. I cant know from missing periods because I haven’t had my period in two months (down to stress probably)!