Hi contramundum -
Without knowing anything about your situation and heeding my own hesitancy to offer any “specific” advice (knowing my own lack of ability in that area), I would say this: If you’re “hearing voices in prayer” you should talk to a priest right away.
The saints teach locutions can come from 3 sources: our imagination, the devil or God. 2 out of 3 of these are bad

so the “general” rule of advice given by the saints regarding any extraordinary event (visions, locutions, revelations etc) is to ignore it.
It is often beyond our ability to discern on our own where these voices come from without a competent guide. And if they’re from God, don’t worry, He won’t be offended if you turn away from them . . . He’ll simply make known to you what you need to know through some other means.
Dave.
PS - If you’re not talking about locutions but inspirations, you might want to take a look at MommyOf4’s post for a good checklist you can apply to your situation prior to reading some of the books mentioned in this thread . . .