I am a 5'4", 114 lb female, age 20. I first got my period at age 12 and have never missed a period. I will be 21 in a few months, but I am concerned because I am more than a week late, a concern I have never dealt with before. I am typically very regular. I have started working out after a long period of not doing so, but only a couple times a week and not very high intensity. I have trouble sleeping through the night without waking up once or twice. I have a loss of appetite. I have been extremely stressed lately, but have been doing all I can to try and avoid being overstressed. I took a pregnancy test a couple days ago and it came back negative. Some days, I will sleep all day because I am so exhausted. A friend suggested looking into thyroid problem symptoms, and I was wondering if I could possibly have issues.