What dose it mean when you spot before you menstrual?

So me and my partner have unprotected sex all the time he ejaculates in me all the time I use wild yam as birth control and its been successful for 4 months. But Wednesday we had sex we both wanted it but I was dry even with a lot of lube it was real hard for me to open. It didn't really hurt after i was spotting I thought I was on my menstral but it stopped. and today I came on my period like I was supposed to. Im extremly regular. But im curious to know want that spotting was??