What Causes Dark Spotting Between Periods And Tenderness Of Breast?

I HAD NORMAL PERIOD ON THE 15 OF JUNE BUT ON THE 14 OF JULY I STEARED TO HAVE BROWN SPOTTING WHICH TURNED TO A LIGHT RED THEN ON THE DAY MY PERIOD WAS DUE I HAD A SMALL FLOW OF BLACK LIKE BLOOD I ALLSO FEEL SICK AND HAVE TENDER BOOBS IT IS NOW THE 21 OF JULY AND I AM STILL GETTING LIGHT RED BLOOD WHICH STOPS AND STARTS.I AM TRYING FOR A BABY