Chemical Pregnancy

Karen • Trying but not trying. If God wants us to have more children I’m open to it. Already had two mc. Our oldest is 17. Mostly now using it for tracking periods.
Hey ladies... I'm pretty sure I'm having a chemical pregnancy and think I have a couple times before. 
I read up on it and the symptoms check so my question is, how many can a woman have before it becomes an issue? Is the only reason the pregnancy is considered chemical because the egg didn't attach correctly? 
Are there ways to prevent these? 
Would your cervical mucus have anything to do with it? 
Thanks in advance.