Any big change in vaginal discharge should be reported to your midwife/OB. I would give them a ring and let them know that this is going on.
this is a normal part of pregnancy, as long as its not itchy or has an odour your fine, its just how your body is reacting to all the extra pregnancy hormones etc, I was going to suggest that if its worring you use pads but it seems your already doing this, just make sure you "äir-dry" the tops of your legsa really well to help with your rash and maybe wear a dress until it clears up