I got my periods again 6 days after it ended

Hi Ladies,

My period arrived on the 3rd July 2011, Sunday and ended 7 days later 10th July 2011. my periods normally last 3-4 days only but I had heavy bleeding during this week. I now have received my period once again 6 days after it ended 16th July, Saturday its heavy and lots of clots too, normal cramps in the abdominal area. my husband and i had unprotected sex only once during the 11-15th July week. Can any1 possibly tell me whether this is normal or should i concider a doctor ... i feel perfectly normal its just the unexpected period thats my concern.... please help!