Just finished my period a week ago and bleeding again bright red blood why?

Multiple causes: This could be pregnancy related, or it could be related to some anatomic change, such and a uterine polyp. It is worth talking with your ob/gyn and getting in for an evaluation and ultrasound.

Several possibilitie: There are several possible reasons to finish a period a week ago and then get bright red bleeding. If the bleeding is light for 1-2 days could be ovulation bleeding. Blood could come from the uterus - polyp or infection, from the cervix - a growth or infection. Hormones could be off causing irregular periods. If it doesn't resolve get checked.