What Causes Mucous Discharge From The Vagina?

My period started on 20th october and ended on 25th october...After 12 days from the starting date i felt slipperey mucus in vagina...Took ovulation test by new choice...But there was only one line in control line no mark in test line...so i think it was negative...Again took 1 test today again came negative...Dont know what to do...Still feeling slipperey mucus in vagina....When would i ovulate...on which date...plz help me...