Brownish/yellowish/redish discharge ?

I was having back pain since this morning , when I went bathroom I noticed brownish discharge on my underwear. After I peed I wiped myself and the tissue was brownish with a bit yellow and a bit red . I'm 39+4 , is this normal? Having really bad back pains , they aren't stopping . It isn't thick , so I don't think it's mucus plug. It's something they would happen after your period is done but you still have discharge .