Covid vaccine cause false negative?

Can a covid vaccine cause a false negative?? My bf and I both have the same symptoms, headache, body aches, runny/stuffy nose, diarrhea, etc. His pcr test came back positive, mine came back negative. He’s not vaccinated, but I am vaccinated. There’s no way I don’t have it. His symptoms are worse but I chalk that up to me being vaccinated and him not. But I still feel like complete butt!