It's not unhealthy. When you use continuous birth control to skip your period, the lining of your uterus becomes very thin and unstable, which can cause spotting. Seasonale gives you a break every three months to minimize this effect, but it still happens for some women. I think in your case it was probably also affected by missing a pill (or two, I wasn't sure from your post). Personally, I'd keep going and see what happens after your period.
Hi -- I'm on seasonale & when I miss two pills I start bleeding.. usually only for a few days, but everyone is different. Anyway, I agree with Monkeyflower...
Just keep taking your pills (hopefully the bleeding will stop) & then you'll have your "period" and hopefully you'll be all set when you start your new pack. If you start bleeding excessively, I would call your DR just to be safe.