Say you have been with a girl for 6 months and you give head and have sex and love eachother and whatnot etc etc, but she never gave head. How can you talk to her and ask about it?
I have tried asking before and made a bit of an issue about it but I don't think it did anything good.
I don't know how to bring up the subject again in a way that is not to direct or harsh or watever. What do I say? Should I just shut up and never get head? I need some advice. 
Well, I am bisexual, so you are not silly either way. Men are much more likely to spontaneously perform cunnilingus than women are to perform fellatio. With a little pressure on his shoulders, I have usually been able to get what I want.
Tell her that oral sex is an option. She may not be aware that some women actually suck on those things. Get some dry condoms and ask her to try it that way. Above all do not surprise her with a mouthful until she gets used to the idea. If she starts with sucking and finishes with her hand, after your warning, you are most of the way there. Be spotlessly clean.
I can talk rationally about it, I am just not sure as to what to ask or say??
How would you feel if a guy never gave you head? What would you say to him to understand? (btw, i'm hoping you're a girl otherwise im going to look silly now)
We each have our learning curves and a set of comfortable behaviours. She is evidently not there yet. If you cannot talk rationally about it, it is not going to happen.
Perhaps she would be willing to do so with a condom. Or take you close and finish by hand. Or maybe she cannot imagine a penis in her mouth. Lots of women take that position. Talk about it - calmly and rationally.
BTW, among all species of animals there are many more in which the male gives oral sex than in which the female does.