Most doctors advise finishing your current pack and going through your placebo pills then starting the new pill like you would start a new pack of the old one. Starting mid pack can throw your body off more than necessary.

I agree with opal, however, because seasonique doesn't really have inactive pills and because the active ones last so long, I would just switch, start on the active loestrin pills and take them like normal. It wouldn't hurt you at all. I'm not sure if you would need to use a back up method for a week... you might, I'm not sure how different seasonique is hormonally.