What just happened down there..

I got out of the shower and felt something strange down there, it tried out to be a jelled up ball of CM and blood (old looking and dark) I checked out what the inside was like and it yielded the same dark blood and was decently thick. I am still about 15 days from starting my period and am pretty confused on what's going on. According to here, my peak fertility was yesterday, and I had protected sex. I am extra tired today, and have a headache.