What Causes Blood Discharge With Sore Nipples And Cramps?

This is the first month my husband and I have been trying to conceive. My period is always regular but now I am a week late for my period. I have been having cramps like my period is going to come any minute but nothing until yesterday. Yesterday I had some brown coloured stuff on the tissue when I wiped and then last night had blood like my period was starting, so I put a pad on but now there is no blood at all. Took another pregnancy test this morning, one of the ones you can take up to 6 days before your period is due and that has also come out negative. I've also been feeling nauseaous and off my food but not been sick and my nipples are sensitive. Now I have had some more blood but only when I wipe, nothing on the pad and the cramps are worse.