Can you get hypovolemic shock through normal dehydration (not drinking enough) and/or a heavy period?

It would be very: hard to develop hypovolemic shock from dehydration or a heavy period. You might have a low blood pressure or feel tired from anemia but I suspect you would start drinking and/or seek help if you felt that way long before you developed shock.

Not really: Your body is designed with stress hormones that can maintain blood pressure and circulation during these situations for extended periods.If you went past ~10% dehydration (lose 10% of your body weight) in the short term these may fail.