I started bleeding on thursday then friday it was light brown and now it's bleeding again what does this mean?

Vaginal? See doctor.: You don't say where you are bleeding but I assume vaginal. Any new, abnormal, or unexplained vaginal bleeding should be professionally evaluated. There are too many possibilities to guess at the cause in your case: hormonal issues, pregnancy, miscarriage, infections (including STDs), fibroid tumors, and more. Call your doctor and make an appointment this week. Good luck!