J.,
First, I too had a miscarriage in July last year and am now 21 weeks along. I still haven't told everyone, for various reasons, and since I am a bigger person I can get away with it. Emotions run there course due to your hormones, so try not to think about it and let things happen as they should. You are not bad for having the feelings you are having.
As for your clotting disorder, not to scare you, but my son had a stroke in utero and he now has Cerebral Palsy, mild left hemi-plegia. He is cognitively very bright and walking, but has a fine motor delay on his left side. We spend 3 hours a week in therapy and constantly working with him. Him and I have both been tested for blood clotting disorders etc. to try and insure my current pregnancy will be ok. Since you know you have a disorder, why not take the meds to prevent potential problems? Not questioning your decision, just want to let you know of the hazars associated with just letting things happen. We don't know why my son had a stroke, so there is nothing I can do but pray it does not happen again. Just my 2 cents!
-L.