If you took a hpv shot when you were 13 or 12 then you had sex at 14 can it help you not have hpv?

Yes: The HPV shot's goal is to provide relative immunity to the acquisition of HPV.

Should be: If you have had all three vaccines, you should be immune. Of course, all vaccines are not 100% effective.

That's the idea: The vaccine contains the strains that are linked most often with cervical cancer and wart producing HPV. If you are vaccinated it helps produce a protective barrier to these strains. It does not eliminate the risk of HPV strains not in the vaccine and there are many. A newer Gardasil 9 helps against more of these strains.