Is it safe to have unprotected sex 4days after period?

No. Most fertile. : You are most likely to be ovulating between 10 and 14 days from the first day of your period. If you have a period lasting 4-5 days, then having sex 4 days after the end of your period puts you very close to ovulation. That's a high risk time. Unless you're planning on getting pregnant, don't risk it. If you've already, maybe the morning after pill would be a good idea.