I've just turned 23 and I'm a bit worried because I'm missing my periods. Today marks the 8th day they should have started, but there's nothing yet. It's unusual for me since I haven't experienced a delay like this in the past three years. The only time I had a delay was when I traveled abroad in 2013, and it was a 15-day delay. Last month, my period was only three days late. I had protected sex earlier this month, and I even took a pregnancy test, which came out negative. Do you know why this might be happening or when I might get my periods?