When is the safest time to have unprotected sex?

Never really: Even women who have regular cycles and do rhythm, get pregnant. I've seen women conceive on their menstrual cycle. Its just not a good idea to have "safe days". In addition men at your age carry hpv at a rate of about 65-70%. 1 in 5 may have herpes and about the rate of chlamydia in women is so high now that its recommended they get tested at yearly.