i'm in the same boat, have 7. i'm by no means an expert, but a few things come to mind:
1) I know of people who received interviews in january weeks before their scheduled interview suggesting that yes, people do cancel and spots can open up
2) I know of multiple people who have matched with as few as 3 interviews. Of course, this is not ideal and I would freak out if this were my situation, but that's me.
3) I'm pretty happy with 7 interviews... Should I be more worried??
It's so hard to not freak out about this everyday but worrying doesn't accomplish much. It's easy to say that especially when you meet people with amazing credentials and 15-20 interviews but I think we're in a pretty good place...Stay positive!!!