sex ed didnt teach about this..

I am still very much confused about when are the best times to engage in sexual intercourse (of course always use protection either way) Is it before ur period maybe a week before maybe after ur period, a week after? I am just so confused about this and fertility window? I want to ask my mom but i dont want her to go off on me and start lecturing about how I shouldnt be worrying/curious about this cause im too young, but isnt it better to always be informed about this? Id just like for anybody to explain this to me. Also Discharge I know what it is somewhat but i still dont know its full meaning. Please help!