It's most likely your period. A D&C cleans out your uterine lining, so it pretty much re-sets the clock for periods. The lining would have built up a bit slowly and is now sloughing off. I would wait another cycle before trying to get pregnant, if that is the plan, because you'll give your uterus a chance to get totally back to normal.
Yeah it is probably your period from what I read your period usally returns about 4 to 8 weeks after a D&C. There is something about intercourse that helps get the ball rolling with your period if it is close to that time anyway. I had the same situation except I didn't have a D&C and my miscarriage had been over two months ago. But almost right after my husband and I had intercourse close to the time I "should" be having my period I had a very heavy flow and it last for about 5 days (normally my periods only last 3). Although since this is your first period after a D&C it most likely will be light. Do not be alarmed if your next period is heavy than normal for you and if you pass a small amount of clots.