I was on that for a few years when I was younger. When I stopped taking it took a few cycles before I had "regular" peroids. I think I had a few very close together, then I skipped one before I got normal again.
Every woman is different. Be sure to carry the right stuff in your purse, so you are prepared.
Sorry.... Unfortunately, you will prob be buying a lot of pregnancy tests. (the cheap ones work too)
The last time I stopped taking pills I was fairly regular pretty quickly. Each time can be different.
Can't really tell ya when you'll get your period. Some women it takes a while and other women it will come right on time. When I came off the pill my period was late the first few times. Make sure you track when it comes. It could potentially be quite irregular the first few months...it actually took me up to a year or more and I still didn't have my cycles on track completely. Hopefully you'll be lucky and it comes regular.
I would give it the 28 days though and if you're worried you could always take a test after that.