You can only get pregnant during the 4-14 days (depending on your cycles) when you are ovulating (usually happens about 4-14 days after your period is over, depending on your cycle). After that (about a two week period, again, depending on your cycle) you can have sex with no possibility of getting pregnant because you have already ovulated, there is no egg to fertilize.
You are able to have sex, usually, through the second day of your period, third if you have a longer (28 days) cycle.
If you want to know more information about knowing when you are ovulating, check out the natural family planning thread (it might be buried a little). I've typed up detailed information on how to know.
It's easy, once you get the hang of it, it's free, and it's as effective as birth control (99%).
As far as your symptoms go, they sound pretty normal. Coming off bcp can really mess around with your hormones and the natural system your body has. It will normalize eventually.
You can check out these books: the art of natural family planning, and taking charge of your fertility (i think that's what it's called) to learn alternative methods of birth control from the pill.