A negative pregnancy
test can rule out pregnancy quite reliably.A missed period and symptoms that you suggest can be due to many other causes, like stress
imbalance etc. Although there is a possibility of a light period continuing till a woman is 3 months pregnant,as could have been the case with your friend,a negative pregnancy test almost confirms there is no pregnancy.You could get an ultrasound
if you are still in doubt.
As it has been a year since you've been trying, you should consult your gynecologist for investigations of husbands semen and your ovulation and status of tubes.