I just got over a yeast infection. Last night was the first time I had sex since the infection and I have yellow, smelly discharge now. What is it?

BV? Trich? STD? Was yeast infection professionally diagnosed? Or just assumed based on symptoms and self-treated? If not already done, you need testing for STDs (gonorrhea, chlamydia, trichomonas), and for bacterial vaginosis. Colored discharge usually means infection, and strong odor is associated with BV and trichs. See a doctor or clinic ASAP for exam and (re)testing. Good luck!