All testing has came back negative, what would slow down cell turn over in the vagina and cause discharge to pool/thicken rather than exit the vag?

Vaginal overgrowth: Bacterial vaginosis is an overgrowth of normal vaginal flora. The vaginal discharge can increase from sexual activity, from douching ( not recommended), and a host of other reasons, including stress. I suspect this is what you are dealing with. The secretions are typical mucous, which will be sticky and not just "fall out" of the vagina.