Preseed?

I'm on my third cycle ttc and still nothing. My fertile week is coming up and I'm looking into trying out preseed because everyone here raves about it. I started looking it up online and saw some women talking about how it "causes" miscarriages and now I'm worried. It makes sense why a miscarriage could result from preseed, but what are the odds of that happening? And when is it recommended to start using it? I do get ewcm when I'm fertile, but it's usually mixed with creamy. Could that be affecting why I can't get pregnant? :(