I'm 18 and I was on yaz for 3 months because my period would last 2 weeks. But I missed 3 pills on the last pack. And my period came back soon er that planned. Its been 8 days and I still have it. And I have pain in my right side. What could this bee.

Its probably because you missed a couple pills. Because that's sort of what happened to me when I messed up my pills. It didn't last 8 days, but it was heavier than usual and lasted a little longer. I don't know about the pain though, unless its just cramping. But for me my cramps are always lower towards the middle...