You can get pregnant .A.N.Y time

Becuase you ovulate before your period and not after you can get pregnant even before you have your first period.

Unless you are a dedicated, long-term charter it is not possible to know when you ovulate exactly.
Because sperm can live upto 5 days in the female body, then you risk pregnancy anytime you have unprotected sex.

Ovulation predictor kits don't really help as they only show you that you have ovulated - and that's a bit too late if you had sex 5 - 4- 3- 2 - 1 days ago as the sperm are already in there, waiting for that egg to make you pregnant.

So yes...

you risk pregnancy at any time