I think it's normal for it to vary from day to day. Some days I have quite a lot, and some days none at all. And I have read that yellow can be normal, too, but if it has been white/clear and then changes to yellow it can be a sign of an infection. I had yellow CM for about 3 1/2 weeks starting when I found out I was pregnant, and then it changed to white about a week and a half ago. I still have mega morning sickness, so I assume I'm still pregnant. Who knows what my body is doing, though!
Yup, it does get heavier later on. I'm 32 weeks, and I always have it now. Wearing a pantyliner helps keep you feeling drier though. But anytime you have yellow or green discharge, you need to at least get it checked, as was mentioned. But don't freak out if you do have it, cause I have yellow discharge at times, and have gone to the dr a lot for it, and it has pretty much always been normal. Only 2 times was it from a yeast infection. So hang in there, you'll get used to it eventually!