Can Boric Acid Kill Sperm And Prevent Pregnancy, Even Though I Had A Faint Pregnancy Test Result And Bleeding After Sex?

Hi, I’m having a pregnancy scare. I took a boric acid after learning my fiancé sperm entered my body. Is there anyway that the boric acid killed all the sperm & I’m not pregnant? I had a faint line in my pregnancy test and my HCG level is 0.6 . My period is due in 9 days & I had sex two days ago and after the sex I was bleeding. I have no infections all my blood work is negative & my cervix is good.