Headphones not loud enough

I'm not certain what I may have done . I'm recording a vocal and as I'm doing that , I'd like to hear more of the vocal . After it's recorded it plays back fine. But hearing myself as I record better would be nice. On other tunes things worked Ok ..

I plug my Mic into a Presous Firestudio. If I turn up the head phones it seems to turn Everything up.

Any ideas what I should check ...

Thanks & Peace