Thanks for visiting HCM.
with yellowish discharge certainly means infection and it's possible to be a sign of STD. You must visit your gynecologist to sort out the problem. You may be needing a gram staining, culture and sensitivity examination of the pus.
Till then you can take antibiotic as per the syndromic approach of STD which constitutes combination of azithromycin
150 mg, tinidazole
2g...all in a single dose... BOth of you will have to take the antibiotics..