I've been wanting to be a female for about 4 years, I've never had a proper relationship with a woman, somehow it doesn't feel right to do the man's thing and chat up women when you feel a lot like one inside, although I still fancy them like crazy, how do I get around this and what would I tell her about my gender feelings? 

It all depends on the women or guy if they are looking for a guy then yes it would effect the relationship.  I always been honest with my gender might not have spilled it out right away but before things got serious.  I never acted like a guy while dating always been myself.  If they like who you are then there would be a second date if not then they were not the right one.  You do not want to live a lie and have the truth rip apart the relationship years into it.  The truth has a way to come out sooner or later.  There are women who like feminite men have faith you will find one.  My wife found me when I was not looking at women. 

It honestly takes a great lady. Very thankful I have one. It is hard for her to understand sometimes, but I will give her time for it. With me, and my constant thoughts of wanting to be female, I become very quiet and depressed. Soooo, I have to work very hard to let her know how special she is and important she is to me. Thats a key thing.