Suggest Treatment For Blood Stained Vaginal Discharge After Having Intercourse

Hello, I m a 29 year old female with pcos. Lately, after intercourse or any sexual activity involving insertion into the vagina is causing bloody, stringy discharge immediately after activities. It can last anytime between right after to 3 days later that i have the discharge. This only just recently started happening. I ve taken a pregnancy test twice, which has come out negative and i have mirena (hoped it would make me regular but i now never have a period)