Has others have already put here, the problem and this is important is not your GF, it is you.
Remember that.
Somewhere in the relationship, you allowed yourself to be predictable, probably thinking such things like "I need to keep her happy". Stuff like that, don't worry most guys here have been there too.
You see some guys in relationships try to make it 'work', but they make it work around westernised feminized brainwashing. Successful marriages if you look at them and relationships, the guy is usually some sort independent entity whow is the head of the relationship, he is in charge, and the unsuccesful ones have the guy walking around like a pet dog to some ball busting bitc*.
Your setting yourself up for the latter.
In future relationships you need to be concurent with the male core inside, and make zero apologies for doing what you do. Get rid of the nice guy, white knight keeping her happy bull-shi* and concentrate on keeping yourself happy. You can be a nice guy, but not the boring predictable got to please her no matter what and she is right about everything and she can do no wrong, nice guy.
Women sh*t test in relationships, they chip away at your male armor and at some stage you allowed her to strip away yours and it turns them into bitter shrews. Women chip away, but they are never happy with the results if they are succesful.
Or you allowed yourself to settle for second best or a women with red-flags because it was available.
First port of call is to stand up to this shrew, pay her back in kind, seriously her bratty actions should be religating her to garbage in your mind. If my girl acted like your girl, I would seriously be thinking of replacing her, rather then arguing my case.
At least your on a better path, you have been rewarding her shi&&y atitude by begging for sex and rewarding her for treating you like garbage by being more needy, probably scared to loose her, when on the contrary you should be getting pis*ed at her bratty attitude instead.
Give her the gift of missing you, seriously in this situation I feel if you want a testosterone shot, get out there bone another girl. Then you wont be complaining to your GF your not getting sex, instead the more she acts like a bitter cun*, the more you'll want to tap the other girl on the side. That to me is the best cure.
Your girl is acting like a bitter shrew because she has your armor chipped to chump. The best injection is to get your balls stroked by some other girl, that will infuse your male core with the aloof A-hole your current GF secretly wants, that all women want, but never admit it.
Man up, or if this relationship carries on, your GF will at least be: Fat, watching Oprah whilst you come in from a hard days work. The type of couple you see when your out in supermarkets, the Fat ugly ball-busting looks like she is swolling a wasp, towing the guy behind her, who looks like an emascualted puss*.
Further edit:
for starters start thinking about being the discission maker, even stupid things like going out for a burger. She gives you some run around, for example you toss her two examples, she says she doesn't know. Make the choice for her. Even little things like this add up, take charge, make the choices, make the decisions. She wants to decorate the house, she aint doing shi* till she has run it by you. Be the man, be the one she has to look up to, the one she has to get permission to do things for, the one who makes decissions for her.
"Shall we head to the pictures or go out for a meal.
You say
"Let's go catch a film there is this horror i want to see"
Even if she doesn't like horrors.
Seriously, women lable this cra* has ars*hole, but they get wetter then April, when they are lead.
Lead the bitc* the rest will follow, but first you need to get back your authority, so far she has stripped it to chump that is the hardest test.
You want sex on tap? You need to be the man of the fuc&*ing house. It really is that simple, women do not ge wet fot beta's, they keep them on for emotional and financial support.
Also take the pis* out of her, yes that is right, she does something dumb, bust her as* on it. You'd think this was counter productive, most westernised feminsed pus** men do. But that shi* is like a silver bullet, every guy should bust on his girl at least once to 3 times per day.
When you get in from work tonight, walk in the door and say this 'Hey chunky bum, is my tea ready'.