本人為乙型肝炎帶菌者, 但是最近驗血B型肝炎表面抗原卻呈陰性反應.為什麼?

You see consult with a doctor.

There are 2 possible issues:

1. The test was inaccurate; or,

2. You are no longer a Hep B carrier.

Either way, a doctor should be able to confirm this for you.