letro should start to kill E within a few hours. if your lean enough you can see it dry you out over the course of the day. sensitivity should go away in a couple of days.
How long did you have it before you stated the letro? The later, the longer it will take to subside.
you may need to run it at 2.5mg/ed for a month or more. depending on how "set in" your gyno is.