How did i get a yeast infection from my boyfriend?

Normal flora: We are all colonized with bacteria and fungi (we are buggy!). The organisms can be transmitted a via skin to skin contact. If your so had inflammation of the head of the penis (balnitis) this needs trestment; if he is uncircumcised he may well have a chronic asymptomatic low grade infection that needs treatment. You as we'll carry these organisms and may be translocating your own flora.