I had sex Sept. 29 and Sept. 30 my last menstrual was Sept. 8th and I was expecting my period oct. 6 but it is now Oct. 9 and I'm late. When can I take a HPT and get accurate results? Cause I only had sex 10 days ago and now 3 days late which by the way I am NEVER late.

You may never had been late before, being late is actually very common. Often stress, worry, infections or other problems

You should wait for about 10 more days to test, ( although false negative can still happen)
Then try every week, till time for next period.