SPOTTING W/O BIRTH CONTROL

I was had spotting yesterday, thought it was my period so I put a tampon in. When I went to take it out there was just white discharge on it, no blood. No blood this morning either. It was a significant amount of blood as well. The thing is, I am not on any form of birth control and have not had sex. I have had regular periods for about 5-7 years. What could the spotting be?  I've never had it before.