If a breast excrete a liquid, is this a sign of pregnancy?

Not necessarily.: Possible causes for galactorrhea include but are not limited to use of birth control pills, tricyclic antidepressants, antipsychotic meds, some sedatives, fennel, anise, fenugreek, some hypertension meds, cocaine, opioids, hypothyroidism, prolactinoma, renal dz, pregnancy, testosterone deficiency in men ; significant breast stimulation. Take a pregnancy test if you have missed your period.