I heard something interesting today don't know if it's true or false.
I heard that if a dog tested positive for lyme & anaplasmosis with the snap test but has never been sick from either, so in my mind that means they carry antibodies, so what i heard is if a dog tested positive even if it's never been sick it will decrease fertility.......any thoughts on this subject?

Any parasitic deceases, especially tick born decease can potentially cause infertility. It can also affect any organ in the body, so the dog might get blind, anemic, lame, etc.
There is no way that you can be 100% sure that the dog has never been in contact with at least 1 tick in its life.