So freaking confused!!!

Ok so I started my period like normal and Glow was dead on in predicting it again (love this app) and I was on my period the normal 4-5 days and then I was off for almost a week or and then today I went to the bathroom and there was brownish blood slight reddish blood when I wiped but enough it was enough to have to wear a regular tampon...my SO and I had unprotected sex on the 17th which was my most fertile day of ovulation...so has this happened to anyone or someone know what could be going on?