I am female, 51, 135lbs, normal to low bp, no aenemia, exercise 5x week. Have been experience intermittent pressure and fluttering on left side of abdomen (feels as though my heart is beating in my stomach instead of my chest) followed by feeling of throbbing on left side of neck and increased head pressure and lightheadedness (as though someone was squeezing my neck). Occurs daily, most often when lying down.