(HIV Anxiety) Test result handling by lab tech.

I have tested for 3STDs and HIV on my 12 weeks after exposure at a privately owned and licensed clinic.
I got it back and they are all negative.
However, I have started to concern if they really did the tests or just report negatives for all the tests without really doing the tests.
I know it may sound paranoid/crazy but are they liable for the falsely reported test results?
Should I retest in another clinic/hospital to re-confirm my status?
I am starting to get worried all over again.
Help.