Since the pregnancy test is negative,it is less likely that you are pregnant,but still we can't be sure.
So I would advice you to go for ultrasonography
of pelvis for confirmation.
The symptoms of vommiting and diarrhoea which you are experiencing could be due gastroenteritis
if you have had outside food.
I would advice you to use proper contraception
to avoid unwanted pregnancy, if the sonography report turns out to be normal.
Meet your doctor with the report as soon as possible and also for proper contraceptive
Don't worry, take care