What Causes Delayed Periods With Sore Breasts And Discharge Through Nipples?

my husband and I have been trying to conceive for a month. I have missed my period by 7 days now, my boobs are enlarged and quite tender, I have suffered a few headaches which i dont normally get, have had really bad mood swings and my back has had an outbrake of spots all over. I completed a HPT a few days ago but it was negative, i know i may be pregnant but i also may not as it could be too early for my body, i eat well and excersise. I dont smoke and have not drank however today when i sqeezed my breast a tiny amount of milky fluid came out, i have not had this happen before? it really was only a small amount and didnt leak on its own. Any ideas? very early pregnancy sign? normal hormone issue or something more sinister?