Had myometcomy to remove a fibroid. Found orange discharge after sex on third day of periods. STD?

I have a myometcomy to remove a fibroid 3 months ago and was given hormone treatment right after to help avoid scaring. Since then I had spotting only at the time was cycle was due. My doctor checked my lining 2 weeks ago and said it was thickening well and that I should expect a full period this month. She also said I was just about to ovulate. I am now 3 days late for my period. Last night right after intercourse, I wiped and found yellow/orange ish colored discharge . There was no sign of blood and the yellow/orange has NOT continued. There is no itching, burning, or anything else. I do have more normal looking discharge than normal though. Any idea what caused that weird discharge? I am positive it is not an STD .