Std testing

How accurate is a std from a test from a clinic at home test ?

My bf had a test and it came as negative , I had a test and recieved it today and it came negative . But my bf has had symptoms of something and I haven’t . He went to the clinic today and they said he could be postive of an std and have gave him antibiotics. But I am negative and the last time we had sex was 3 weeks ago I am confused and don’t know what to do