You aren't really protected on the pill until you've been taking them for a minimum of 7 days (due to a personal decision, I always wait a month). So, in the first 7 days, you should be wearing a condom during sex to protect from pregnancy.
However, you took Plan B, which is good. It works for situations like yours, so you should be safe.
You should expect your cycle to be a little off. You may bleed earlier than expected, you may not bleed at all. I would get a pregnancy test just to be prepared if you are nervous.
It seems to be you should be fine, but you're not out of the clear. You've done all you can to prevent a pregnancy, now you have to wait and see.
Good luck, and get the test!