How can i tell if i broke my hymen or had my first period? i was fingering myself and quite a bit of bright red blood came out.

Hmmm: Most likely you tore or cut something, possibly hymen. If hymen bleeding will stop rather quickly. A period would be prolonged bleeding and dark blood versus bright red blood.

Bright=torn tissue: Bright red blood would be from torn tissue and that could be from a torn hymen or any nearby tissue you scratched. Menstrual blood is quite different in color and consistency.