There is a chance for pregnancy during any time of a woman's cycle, but more so during the fertile days. If your period cycle is usually 28-30 days long, then your fertile days should be around day 14-15 or so which would mean day 10 onwards to about day 20 would be advisable to use protection. However, days 12-16 or so would be actual fertile days
You had unprotected sex on day 8, so like i said, if your cycle is usually 28-30 days long, you should be fine, but if it's usually shorter than that, then you may have had sex closer to your fertile days and since sperm can survive in our body for 5-7 days, there is a chance. I hope this makes sense! All the best!