HIV :: Detailed Test Negative - Preliminary Borderline Positive

I do not know what is preliminary and detail, but according to the health department of my country they should be ELISA and Western Blot.

So I was doing a routine physical, and the doctor suggested to check for HIV since I told him I am planning to have a baby. I have never engaged in any risky behaviour* thus no exposure.

Result came back and I was told the preliminary is borderline reactive but the "detail" test is negative. He asked me if I had done any of those risky things again. After I told him no he said I should be fine and shouldn't worry, but I should come back a month later to reconfirm. He did not ask me to take any precaution - which is kind of weird if you are asking someone to reconfirm a month later...

The only thing I considered with any "risk" is blood test, which I am always paranoid that the nurse "forget" to use a new syringe, either by accident or on purpose. But then my last blood test was done in May so if anything bad did happen I should be seeing a full positive/positive result..

I was googling and my situation usually comes to either:
a) recent infection
b) false positive
c) clinical error

Given my situation:
1) No risky behaviour
2) Has mild autoimmune disease (one of the possible factor to distort the test result I heard)
3) Never has any acute HIV infection symptoms (get a cold here and there, but it is always during the time where half the office is sick and never high grade fever)
4) Just a borderline result for ELISA, and negative Western Blot

The odd should be in (heavily) my favour, right? I am just mad that why don't they just do a viral load or similar test, instead of leaving me in paranoid for a month.