The term for this is cynicicm, and the person is a cynic.
DOUBTing
Thank goodness someone asked that question. Tom's goodness is a sharp contrast to his wife's hateful character.
Doubting
I'm not doubting your story, I just have a few clarifying questions to ask.
what word can I substitute for constitutes
oh my goodness?
Wondering about the veracity of something
I was doubting that she was telling the truth^ In this answer doubting is used as a verb. The word doubting can be used as a verb (somehow informal because DOUBT is a stative verb). It can also be used as an adjective according to some dictionaries (although dubious would be the best word)It was a very doubting/dubious answer (an adjective)
Goodness is die Güte in German
The word goodness has two syllables. Good-ness.
Sanitarium
audience