I Was Having Sex For The Pass Three Weeks Unprotected,

I was having sex for the pass three weeks unprotected, and one morning while having sex my fiancé pulls out and there was this this pinkish color stuff from me , I was due on having my period but I haven't seen it till now I'm having the period cramps but I'm passing a brown color substance with a bad smell and when I wipe like a little blood , what can be the cause of that ?