Pink discharge in 3rd trimester of pregnancy?

i am 30 weeks pregnant and lately i have been having a lot of pinkish tan discharge. Its kind of thick and it has little pieces of tissue looking pieces in it. I know its not toilet paper because even after a shower the tissue pieces are still there. The other night i had really bad cramps and it was after sex that i notices the discharge dripping out. The next day it went away and was clear or a bit yellowish. NOw today it is pink/tan Again. Does anybody know why this is. The doctors tested it to see if it was amniotic fluid and she said that when the cervix starts to ripen that the discharge would change, but i am still wondering whats going on. Could it be pieces of my mucus plug? Please help, i am going back to the dr in a few days so don't write for me to call my mw.