Thanks for your query,
Birth pills have side effects like vomiting
,missed periods,breakthrough bleeding
these symptoms will be disappeared shortly.
test was negative,you need not worry.
Please do not skip birth pills,take these medication as per doctor's advice certainly.
If symptoms persist you better to visit your doctor.
Please take plenty of water and fluids.
Hope I have answered your question.
If you have any queries I will be happy to help you.