What do you call it when others never listen to what I am saying or discredit my experiences and talk over me?
Ignore. Everyone ignores me and my accomplishments. (to be fair, this is more passive than your implied active "discredit").
Condescension is another good way to describe this behavior.
Disregard would be an appropriate word.
Disregard means - "lack of consideration or respect"
So to disregard someone not only means to ignore but it also means to disrespect that person (by ignoring or abusing or back biting or belittling achievements..so the word disregard fits right in your context).
Disregard, ignore, belittle, dismiss, overlook and neglect are all words that would be suitable to use for what you are describing.
From what you are describing, I would go for disregard.