false negatives for std urine tests?

My bf tested negative for chlamydia, while i had tested positive.
i have never been with anyone else, and he told me he had been unfaithful. i had been negative for stds on my prior paps over the years we were together.
it looked like i had cheated due to mine being positive, but obviously something wasnt right because i cant catch an std when i havent been with anyone else.
My doctor told us that it is because he had done the urine test in the afternoon, and had already urinated prior to going to get tested, and it became a false negative because all the bugs had been flushed out.
this contradicts what my bf family doctor had said because he said "there is no way the test is wrong".
so my question is, are there a lot of false negatives due to doctors not telling thier patients not to urinate prior to testing??

[Vance2335]

I can't say if there are a lot of false negative, but yes if you urinate 1hr or less before the urine for the test you might get a false negative. It is best to have the 1st urine of the day or wait at least 1hr...the longer the better to give urine sample.

Maybe you had a false positive?