Your Dc cannot get it from you. It is called a SEXUALLY transmitted infection because it has to be transmitted sexually. The genitals of babies passing through your vagina when you gave birth (I am presuming they were vaginal deliveries) does not count. And consider this - if you have had it for ages, and it affects fertility, as you worry about your DD, then how would you have got pregnant yourself? You are simply not thinking logically, and it makes no scientific sense either.
You do need to see your GP urgently, but for your anxiety and intrusive thoughts. If you are checking google for symptoms, trying to convince yourself of the worst, imagining your children dying from a sniffle, finding it difficult to merely look at your DD without thinking you have ruined her life, etc., etc., then you need help. It has clearly taken over your life. I have anxiety and OCD (the intrusive thought kind, too), so I do know what you are going through.
But please heed this: whilst you are working yourself up worrying about non-existent or impossible awful or fatal health scenarios for your DC, you are actually adversly affecting them. Paradoxically, by obsessively sorrying about protecting them from harm in this extreme way, your anxiety will start to harm them. It is not a healthy, positive way for them to live, and could make them nervous and feel like life is unsafe, etc. Again, I know this because my own mum has always been the same way as you describe. It has really badly affected her children, even into adulthood.