What Causes Delayed Periods Along With Intermittent Vaginal Bleeding?

Hi i got my period about almost two weeks late this month and it was realy heavy for 4days about asuper tampon every 2hours....since then ive been on and off bleeding light pink then bright red then light brown then gone then starts like that again for the past two weeks with no actual stoping completly ...havent had sex since about three weeks before this started...which was two weeks after last regular period what could be wrong?