Advice please 😀

Hello... I have come across this helpful page and was looking for some advice. I'm not great with the abbreviations so bare with me lol. 

Firstly I came off the injection 12 months ago and have had regular periods for 10 months. I started my period on the 13th of Aug and have 30 day cycles, I had intercorse last night and this morning after intercorse both times I noticed a dark red/ brown tinge too the paper towel. Not thinking too much into I carried on my day as normal then went too the toilet after and noticed I had a dark red/ brown blood enough for a pantie liner. Any help would be much appreciated. Xxx