Im in the 5th day of my period and its still heavy,?

ok, like I said Im in the 5th day of my period and its still heavy. not as heavy as the 2nd or 3rd day, but it just seems like the period that doesnt want to go away. also, right before I go pee, I 'll p this one single clot thats the size of a g. I just went to to the hospital, and they did an ultrasound and the doctor didnt see any lumps, cysts or anything that caused him to be concerned. as well, I had some blood work done (hemoglobin) and everything was fine. I dont have any cramping as well, in fact I didnt have that much this time and my period was 3 days early. Im 28 years old by the way and for the most part my periods have been fine except for a few cycles where they were slightly irregular. I am curious if any other women out there has gone through the same thing. hope some one can help me with this!