I had my period on june 1st and it ended on the 10th now its the 17th and i'm spotting... why is this? also i've only had 3 periods and never had sex.

Not unusual: To have irregular periods when you first start. You may not ovulate each cycle, stress and other hormones can affect the regularity of your cycle. If the bleeding is really heavy or you have painful cramps, you may want to discuss it with your doctor.

Dates: It might be helpful to add the months to your question. I'm assuming you're stating that you had a period on 6/1, ended on 6/10, and then on 6/17 you spotted? If so, that's normal. If you've only ever had 3 periods, it can take awhile before cycles regulate. Birth control pills can help to regulate your cycle, if you're concerned. Extremes of weight (thin/heavy) can affect your cycles as well.