“Concerned?”

About 6 years ago I performed oral sex on a girl and I noticed after that she had this whiteish color around the opening of her vagina, the very next day I woke up feeling extremely fatigued, brain fog, I would get dizzy and occasionally feel like I am blacking out for a second. Since then I have lost around 10 kgs in weight and still suffer from fatigue and weakness and get frequent yeast infections on my penis, I also have body pains especially in my knees. I have had HIV Tests as well as tests for other STD'S which have all come out negative. I have also been diagnosed with vitamin B12 deficiency.
I am now in a serious relationship and I have been intimate with my partner believing that I am free of any STD. Since we had sex she has been complaining of dizziness, fatigue, weakness, and feeling like blacking out.

I know all my test results were negative but I am still really concerned that I may have something which I have passed on to her.

Please help me understand what this could be.