What Causes Spotting Continuously With Moodiness, Tender Breasts And Cramps?

I am a 21 year old female. I had my regular period 2.5 weeks ago. I tend to have long periods lasting about 7 days, then another 2-3 days of light spotting. However, this time, the spotting has not stopped. My mood is all over, my braests are very tender, and I'm having cramps, just like I would if I was PMSing, but it hasn't stopped since my last period ended. Pregnancy is not a possibility in any way. What is going on??