What Causes Delay In Menstruation Other Than Pregnancy?

hi i just writing cause so confused, i missed a pill tablet on 11th September, which i ended up coming on a period for 5 days (to the 17th september)so me and my husband decided to try 4 a baby so i came of my pill on 20th september but on the friday 8th October i had a brown discharge which lasted till the sunday 10th only a small amount though, i also had cramps and sore breast which i still have now, i did pregnancy test which said negative, i still havent had a period which i so confused with cause surly i would had a period by now from being of the pill and i done another 3 pregnancy test which came back negative? i also rang nhs help line said go to my doctor but he wants me wait till next week which i so worried at mo in case i have some thing wrong, what would u recommend i could do to find out what going on?