Has anyone experienced this? TMI

I'm suppose to start my period today but instead I'm getting cramps and white discharge (which started yesterday). I had a 9hr trip home from vaca today & there was yellow in my underwear by the end of the trip. I noticed it when we stopped to pee 3hrs into the trip. When I used my finger to check a little bit ago, there was white discharge in my fingernail. Has anyone experienced this?