Thanks for the query.
can be due to gastroenteritis
you are having. It can be due irritable bowel syndrome
Excessive blood loss during periods can cause anemia that can also lead to dizziness.
So you better consult gynecologist and undergo physical examination and ultrasound
to find out the possible cause for your problem and take treatment accordingly.
Possibly by ultrasound the problem with gastrointestinal system can also be made out.
For more details you can ask me through: http://www.healthcaremagic.com/doctors/dr-sree-gouri-sr/63429