Hello dear
I understand your concern
Period followed by the unprotected sex does not cause pregnancy.
Heavy bleeding after the sex could be due to infection/inflammation in cervix, vagina, polyp or any growth in cervix and uterus, cervix/endometrium dysplasia.
Throw up, stomach ache could be due to
stomach infection.
Dizziness could be due to blood loss.
I would suggest to consult the gynecologist and undergo vaginal examination, vaginal swab test, USG scan, PAP smear/
colposcopy to rule out the cause.
Specific treatment will depend on the cause.
Bleeding can be reduced by the
progesterone pill.
Take tablet meftal spas
Maintain proper pelvic hygiene
Take proper rest, eat healthy diet with
iron supplements.
Hope this may help you
Contact further if follow up needed.
Best regards
Dr. Sagar