Birth control and CM

So I’m on the combo pill and I check my CM every day just because. Anyways, I was reading an article that said water CM whIch could be clear or even look like skim milk is the most fertile CM even more so then egg white. Well I take my pill every single day at the same time and I notice some days that I have that skim milk consistency of CM. Does that mean that my pill isn’t working? I’ve never had the egg white consistency since being on the pill, but before, I used to. Do I need to worry?