What Causes Dark Blood Discharge And Foul Odour From Vagina?

I am 47yr old female. I had sex last night and today, and both times, there was an awful, door coming from my vagina, and brownish blood coming from my vagina. I have a cyst in my vagina, and when I saw my Dr about it last month, he took a swab and said I had some bacteria present in my vagina, that it is not uncommon, and it wasn t sexually transmitted. I took a strong antibiotic for 7days. I am currently taking amoxicillin for a dental infection, am on day 4 of treatment. What could be causing the rust coloured blood and awful smell. It s a terrible odour..