E2 is what makes your nips itch and gives you gyno.
You need to have your sensitive Estrogen checked. Dont get crazy especially with the letro because it's strong. I believe you have to tapper up and down with it also but I'm not 100% because I dont use it. A little nipple sensitivity is normal, a little... Obviously if you start to get a lump then you have something to worry about.
http://forums.steroid.com/anabolic-s...-reversal.html