Hello Rocio, Thanks for your query.
In sexually active young women, periods may be normally irregular. Therefore stress on using barrier contraceptives during sexual intercourse to avoid pregnancy
hassles. Because you had periods a week after unprotected sex, pregnancy is out of question. And because you mentioned you generally have heavy periods
for 5-6 days, the most common cause of your dizziness
and nausea may be anaemia. Check your Blood Hemoglobin
levels. Have lots of water and green vegetables.