I had the same issue. If I initiated conversations I was OK, but it was a different story when I had to respond to an unexpected question. For me, it was just a matter of time. Continue practicing. Continue using your 'new' voice. It will slowly improve. Eventually it will become your 'default' voice, and conversation will become much easier. It may take several months, but it will happen. I've often thought that if transition were easy, everyone would do it!
Love always -- Jessica Rose