Hi Jimsgirl,
It happens a lot that women post wondering if a heavy AF, late AF, or large clot, may mean that they m/c'd. Here's a link that might help to put your mind at ease.
http://www.pregnancyloss.info/not_su...iscarrying.htm
As it says here, AF can sometimes just be off slightly for whatever reason and can come on differently with spotting, clots, or heavier or lighter than usual. This is not at all an indication that it was a m/c, though docs are now beginning to think that most healthy naturally O-ing women may well conceive almost every cycle and the embie just doesn't implant so AF comes. I'm not sure if they consider that a m/c or not, but it is thought that 75% of all pr are lost... most before we even miss AF.
But the fact that AF came with a large clot is probably an indication of a corpus luteum cyst which may have been a non-O cycle. Did you chart temps or do OPK this cycle? The clot would not have been the embie... which at this point, had you been pr, would not resemble a clot but would be a tiny sac so small you would probably not have been able to see it at all.
As we get older, its common to have at least one strange cycle like this per year and AF can change a lot in general. After I turned 30, for example, I occassionally noticed some mid cycle spotting that I had never had before. At first I thought maybe it was implantaion spotting, but it turned out to be withdrawal bleeding which can happen more frequently with age. If you don't already have it, I highly recommend getting the Taking Charge of Your Fertility book that can really put your mind at ease when dealing with all these strange things our bodies can do. Good luck.
I don't even know if I belong over here yet or not... 
