I’m sorry, but this a very sad thing to read. It sounds to me like she is calling all the shots here, and you are letting her. You don’t get angry when she refuses yet again? How could you not? You don’t have to fly into a rage, but surely, some emotion is felt–some resentment lingers. I’m not saying that you should be the one calling all the shots etc, but that some mutual compromise is needed. Never had sex outside the bedroom? Never in the daylight or with the lights on (now, I don’t care for sex with the lights on, but sex in daylight? Of course!) Sex with covers? Unless it’s below zero–I don’t like covers(not that my preferences matter here, just saying.)
Have you told her she has a beautiful body–you say she’s confident etc about her body image, but this is sending up big red flags to me. She sounds controlling–not much wrong with that UNTIL–see below.
But the fact that YOU want more, SHOULD factor in. Partners listen to one another and are willing to at least try new things to please one another. She has it all her way–that is not a recipe for long term happiness.
It seems like you have your mind made up. This relationship obviously matters more to you than the trouble of putting up with bland sex, and it doesn’t appear that there’s any reasoning with your girlfriend, so the one doing the compromising is you. And, really, I’m not sure how helpful anyone’s advice here would be for you in that situation, since it’s so terribly personal. How much sex matters to you and how you feel about your girlfriend aren’t going to be things anybody else here totally “gets” after all.
For what it’s worth–and it likely ain’t much–if I had a boyfriend who only liked one position, always insisted on having the lights off, refused to engage in oral, told his friends that he won’t do things he doesn’t like, and he was happy with our sex life so felt no need to change, well, it wouldn’t matter how much of a sweetheart he was outside of the bedroom. He’d be looking for a new doormat. Sex is a two way street. You compromise and give, so that the both of you are happy. Not so that one is happy and one is only moderately dissatisfied. That kind of selfishness in the bedroom implies selfishness elsewhere. Likely, though, the other arenas where her selfishness reigns aren’t as important or noticable to you.
But, that’s just me. What really matters is what you can live with. And if you can survive the bland sex and selfish lover because everything else is perfect for you, then that’s a perfectly acceptable choice.