Skeptical

[Jason Yan]

Of or pertaining to a sceptic or skepticism;
characterized by skepticism; hesitating to admit the certainly of
doctrines or principles; doubting of everything.

[Luis Fok]

associated with [doubting], not [believing], not accepting

[Dianne]

when you are [weary] of [someones] good natured actions; to not wholeheartedly [believe]

[Justin Bieber]

[Doubtful], [dubious], [questioning], and/or unbelieving.

[Hina Muqadas]

doubting that something is true or useful:

[Lanell]

Not easily convinced; having doubts or reservations.