Thanks Knak, but no, I'm not on any meds that thin blood. The thing is, when I DO get hurt and notice it I don't necessarily bruise, so this would have to come from something quite hard. It doesn't point to easy bruising.
However, it hasn't been happening lately, so hopefully whatever it was has passed. I'm going to ask my therapist about the possibility of blackouts though, because this scares the hell out of me.