mucous discharge can be seen physiologically and pathologically.
in physiological conditions like, during ovulation, sexual arousal, before menstruation
and during pregnancy
in pathological conditions like infections also discharge can be seen.
as you are having mucous discharge, secretion from the milk and delayed periods there is chance of pregnancy.
as some urine pregnancy tests
are less sensitive, you can repeat the test or better go for blood test
for pregnancy after consulting doctor.