I've been on the tricyclen lo for two months, I was on the regular tri cyclen before that. I had unprotected sex about a week after my period and I got a bit scared so I took plan b. I usually get my period on the 3rd green pill but I got my period on the second green pill and it only lasted a day. And was a lot lighter than any other period. My period usually lasts for 3 to 4 days? What does this mean?