i follow my ovulation calendar application in my handphone so i can roughly know when to have sex and when not to.. (that is if ur menstrual cycle is normal and predictable)..
according to the calendar.. u can have sex 1-3 days right after ur menstruation and about roughly 10 days before ur next batch of blood starts to flow..
sometimes i tend to follow but most of the time.. i don't.. haha.. i just use it to see when's my period coming only.
but whatever it is, ask ur male counterpart to at least wear a condom to avoid unwanted pregnancy and depression like urs..