I just had my period about a week ago and now i'm bleeding again why could this be?

Irregular periods: Irregular periods are one of the most common problems obgyns treat. If this is one time problem it usually resolves on its own. If this is a recurring problem you should be evaluated. Infections ; hormonal changes can cause spotting. If there is a concern for pregnancy then do a home pregnancy test . There are many options available to help regulate the menstrual cycle. Schedule a visit.

Breakthrough bleed: Breakthrough bleeding is common for most women at some point in their lives. Most commonly it's due to hormonal changes. If transient, then hopefully next period will be normal. If it continues, then consider birth control pills to help regulate your cycle. In addition, sometimes extremes of weight (thin/heavy) can be cause as well. Make sure you're at a healthy weight.