Wondering if anyone has had similar..

My AF was due on friday 13th and i had one very short period.. like an hour or so. But didnt seem like implantation bleeding as had some clots (sorry tmi).

I did a test which was negative but since then and before ive had such nausea and light headedness which is getting worse. My boobs dont feel too tender which is why im assuming im not pregnant but i cant help wondering if i am but my hg3 is just low at the moment. Im off my food but dont feel like i have a bug or virus. Anyone out there had a similar experience please?