You've worried about this for two years? Seems a bit excessive.
As to the test, here is what Oraquick says:
When you take the OraQuick test, you must swab both the left and right side of your upper gums and the left and right side of your lower gums. Each gum must be swabbed only once. You must follow the test directions carefully to get an accurate result. If you are not sure you swabbed your gums correctly, check for a line next to the letter "C" on the test stick. If a line appears next to the letter "C" on the test stick, you will know your test is working and your results will be accurate. This will occur if you have followed the instructions carefully and you have waited at least 20 minutes after placing the test stick in the test tube. If you do not see a line next to the letter "C," the test is not working properly and you will need to get a new test.
Once on each side. But DID you get the letter C on the test stick? That tells you that you used it correctly.
The risk rate for unprotected sex is LESS THAN ONE PERCENT so being sad and worried is not really warranted.
If you used the test incorrectly and feel you must, do it again following the directions explicitly. But if you got that C, trust your result. Don't make this dramatic or that big of a deal. If you turned up positive, I'd be in utter shock.
If you got the C on the test, trust the result. If you didn't, retake it and do it just as the instructions say and trust THAT result. Tell your anxious brain to be quiet. People have sex without freaking out like this all the time so know that this comes from anxiety and not from logic.