The yellow is the mucus i asked my.doc about it and he said as it gets closer the baby is resting more on your cervix which is pushing out mucus completely normal
In the third trimester you produce a lot more discharge, enough to wear a pad throughout the day
I'm 37w 5d and still having allot of discharge...as the time gets closer the discharge comes out more and now it's yellow and greenish
im 35 weeks today and I have been doing the same thing and its like a lot of it