What Causes Light Spotting With Dark Vaginal Discharges After Intercourse?

Hello im a 26 years old female trying to conceive a baby for a while now,after 2 years of not getting pregnant i went to the specialist for tests,semen analysis,hormonal tests,histerosalpingografy,histeroscopy,all tests were good except my hormonal tests showing i have some thyroid problems currently taking euthyrox 50mg everyday and my hsg showed my tubes are blocked from the base(uterus)then my doc recomanded a histeroscopy to try and unblock them and check my uterus and ovaries,everything looks good it showed my tubes weren t blocked and the doc said maybe it was a spasm,I have a regular period 28-30 days and proven ovulation by Eco,the month of August had sex in the fertile period but my period came exactly when it suppose to (28days) but it was very bright red and very little like 1/4 of my normal period that lasted only 2 days the 3 day I only had like a light spotting big as a coin,a day after period ended I had a vaginal secretion very dark like dark brown,should I be worried?i wanna mention this was my second period after histeroscopy.im currently in vacation and I can t reach my doc.