Sounds like a yeast or uti
I'm 27 weeks and experience the same thing. Although its never really yellow just a white clear discharge. I was just as irritated as you, so I asked my doctor and its completely normal, because our hormones and everything else is changing its bounds to happen and may increase the farther along you get. If any concerns just go get it checked out :)
Discharge is normal before pregnancy and increase in discharge is normal during pregnancy. The color though does indicate an infection. Any odd smell or irritation down there? You should get checked. They are easily treated but do not let it go untreated, it can cause other problems.
Any type of discharge that you are worried about should get checked. However, discharge is normal and varies pregnancy to pregnancy, and woman to woman. I live with panty liners in my underwear, they are a life saver !
If it's yellow, it could be an infection. I'd get it looked at!