My daughter is going through her first period, and it has been going on for 2 weeks and yesterday and all today it was very heavy.

Your age is 20: and you have a menstruating daughter? This is confusing. If you are asking for a 20 year old that is a very late age for a first period. If you are 20 it is unlikely you have a daughter old enough to menstruate. A period this long and very heavy should warrant a visit to her physician.

Asking for someone ?: Initial cycles in 10-14 year olds are often driven by longer term buildup of the uterine lining by estrogen.Since they often don't release eggs for the early cycles, the hormone generated by that process is not around to set the clock for menses. The longer buildup equates to heavier or longer flow. If worrisome & the kid is pale, have her evaluated. Heavy blood loss can result in anemia.