Hi and welcome to HCM!
Thanks for posting your query here.
The ovulation will occur on the 14-16th day in a normal 28-30day cycle. Hence the period from 10 to 20th day is taken as fertile period. If the sperm enters the vagina at this time there are maximum chances of getting pregnant.
In your case it is on the 8th day so there are less chances of ovulation. All the factors using condom and pulling out before gives a less chance for the sperm to enter. Hence you no need to worry.
If still the doubt persists a pregnancy
test can be done on the first day of missing period.
Hope this is helpful to you.