I made it into the top 16, and got an invite to nats ^_^
You know you can still go to nationals though... There's a last chance qualifier in indeanapolis on july 8th, I think. The day before registration. I think my friend might be going to that.
You do it until you hit your seed, of course. If you get no matches you just have to try again. If you're doing everything right that shouldn't happen, though.