Suppose that $X$ is a projective threefold  with at worst conifold singularities  and suppose $\omega_X$ trivial. Suppose $Y$ is a projective variety with a birational morphism $f: Y\to X$  which is an isomorphism away from the conifold points and such that $f^{-1}(p) = \mathbb{P}^1$ for each conifold point $p \in  X$.  Can I conclude that $Y$ is smooth? i.e. that $f:Y\to X$ is a conifold resolution? 

This seems too good to be true, but I was unable to come up with a counterexample and it would be really useful (to me at least) if it were true.