My period has been very regular for the last year, and was very heavy until November when it was shorter and lighter than normal. It is now approx 20 days late. Home pregnancy test came back negative, and I have not started/changed/stopped a hormone based birth control. I regularly feel fatigued, no matter how much I sleep. I have been experiencing cramps and mood swings. Bowel movements have increased and are often looser, but then days of constipation. I struggle to concentrate either at work or reading/watching a movie etc. I tend to be a lot more thirsty than usual. I started exercising more frequently about eight weeks ago, gradually building up to running 3 miles a couple of times a week. I m 24 years old, 5 3, about 135lbs.