1) Disbelieving 2) Distrustful 3) Incredible 4) Like a doubting Thomas 5) Not credulous 6) Sceptical 7) Shocked 8) Skeptical 9) Unbelievable 10) Unbelieving 1) Disbelieving 2) Distrustful 3) Incredible 4) Skeptical 5) Surprised 6) Unbelievable 
• (a.) Not credulous; indisposed to admit or accept that which is related as true, skeptical; unbelieving. • (a.) Incredible; not easy to be believed. • (a.) Indicating, or caused by, disbelief or incredulity.
In·cred'u·lous adjective [ Latin incredulus . See In- not, and Credulous .] 1. Not credulous; indisposed to admit or accept that which is related as true, skeptical; unbelieving. Bacon. « A fantastical incredulous fool.» Bp. Wilkins. ...
skeptical unwilling to believe 
[adj] - not disposed or willing to believe
incredulous 1. Unbelieving; not ready to believe; sceptical. Formerly used of religious unbelief, but no longer applicable in that sense. 2. Unable or unwilling to believe something or completely unconvinced by it.
adjective not disposed or willing to believe; unbelieving
not credulous; disinclined or indisposed to believe; skeptical. · indicating or showing unbelief: an incredulous smile.
not disposed or willing to believe; unbelieving[SAT terms] not disposed or willing to believe; unbelieving