Missed period after Mirena IUD removal?

I got my period about 3 days after I got my IUD out, it's been a month & now I am 4 days late on my new period... I took a pregnancy test the 2nd late day and it was negative. Any ideas?? I have been having LOTS of clear, stretchy mucus- enough that sometimes I will stand up and it will drip down my leg. 😐