Hi.
Noted the history about your boyfriend having red spots on penis which went away on using protection during sex to reappear after unprotected swx.
This is called
balanoposthitis and being transmitted from you to him as per the history you have provided.
Since STDs are negatives there seems to be some sort of
vaginitis although you are asymptomatic.
Hence I would advise you to consult your Gynecologist for clinical evaluation, internal examination to see for any internal cause.
Both of you need to take a course of an antibiotic,
metronidazole, probiotics for 5 days.
Use protection all the time till both of you are cured.
Keep personal hygiene well. Use Liquid
Betadine after sex after cleaning the area well with plenty of water.
Once the course is completed and after a gap of 2 weeks get yourself checked again for internal examination and see for the results.
Hope I have answered your query. Let me know if I can assist you further.
Regards,
Dr. T Chandrakant,
General Surgeon