Pregnant bleeding/cramping off and on this week.........?

Im about 6w and 5 days pregnant. Ive been experiencing light bleeding/little clotting at the beginning of the week and went to the doctors yesterday to see the sonogram and it showed the baby and the flicker of the heartbeat. The following night I experienced heavier cramping and more blood. I saw some clots that were dark and some were grayish. This morning I woke up with just a little more and now its just very faint brown spotting. Im very confused on what it could be...anywhere from a miscarriage or a hemorrage perhaps? If anyone could share their stories or insights on some real experiences. Thanks.