repeat the pregnancy
test again. if it comes negative, there may be possibility of other disorders like hormone imbalance
some of the following disorders to be ruled out for it
1-hypothyroidism- so go for a thyroid function test
due to pituitary adenoma- do test of prolactin level in blood
3-anovulatory menstrual cycles.
so consult your gynecologist about these if your next repeat pregnancy test comes negative.