Hi I m a 21 year old girl who s been having for the past week intermittent tightness on my chest, nausea and slight lower back pain. In addition, my period which is usually prompt is late by three days and I had, but have no longer, diarrhoea. I measured my heart rate and it was an astounding 100 BPM. I am not overweight, I am not overly active but walk about half an hour a day, eat healthily etc. I suffer from mild anxiety and depression as well as bronchitis but have never had physical symptoms before. Looking for answers from seemingly random symptoms.