Is it normal that i want to be a girl?

I am a 27 year old guy, who has always been comfortable with being a male. but lately i find myself wanting to be a female. i love the attention they get and the clothes and hair and make-up. i don't know if i want to get an operation to change my sex. but i think i would be comfortable crossdressing since i like to wear women's lingerie when i pleasure myself. i don't consider myself gay. i sometimes feel like i'm a girl on the inside. these feelings have only surfaced strongly like this about 4 or 5 years ago, but i used to try to ignore them. is this normal?