Am I Asking for Too Much?

I have been with my girlfriend for three and a half years now and we have a great relationship. I am twenty-six and she is twenty-three. I love this girl so much and know without a doubt she feels the same way. We have lived together for almost two years now and that has also been a great experience I do not regret at all. For the first two years of our relationship, we would have sex almost every day, sometimes multiple times a day. It was absolutely great. Over the last year or so, this has tailed off drastically and over the last six months. It has sometimes come to one encounter in a two to three-week period.
We are pretty open with our relationship and we have talked about it. But the situation really came up when my girlfriend walked in on me masturbating to some porn pictures. She became very upset, yelled at me, slapped me, and made me feel like I cheated on her by doing this. I do not think that my occasional porn viewing is wrong, but I can understand where she is coming from. I know that she is insecure about some things, and not just this. She absolutely despises my ex-girlfriend who I have never brought up in any positive or negative way. She is upset that I do not hate her, that my family still converses with her and all of that good stuff. Other than she is a girl whom I loved years ago and I wish her all the good luck, I could care less about her today. I think that it is insecurity, but maybe I am wrong.
The aftermath of the porn incident resulted in me telling her that I felt she wasn’t there for my physical needs and I looked at the porn to get off. So a couple days later, she surprises me with some lingerie, which I loved, and we had great sex for probably eight or ten days. Then the whole thing tapered off again and we went another few weeks having sex once or twice. So I confronted her again about the situation and we had a big fight, which resulted in another week of great sex and tapering off. Another confrontation led to buying some books about loss of libido, which lasted for a week and then stopped. We also bought books about sex tips, how to keep things interesting, and a book with a lot of insightful questions we each answered to get to know more things about each other.
Another confrontation about this led to her going to her doctor to get tested for testosterone/estrogen levels and other things that might drop libido, which resulted in nothing. Then she switched birth control medication and that is where we are now. I would say that the frequency has slightly increased after she has been on the new BC for a month, but we still go a week or two in between though sometimes.
Everything about her turns me on, so it is really hard for me to not be excited. She is beautiful and I let her know that everyday. Our last two encounters were amazing, lasting about two hours each time. The most recent one I methodically planned out with a series of notes taped around the house with instructions. Then she had to sit in the living room with a blindfold on and wait for me in a candle lit room. We both loved every minute of it and she even asked aloud “How can I not want this all the time” with a heavy breath. She tells me it is not me at all and that she is attracted to me, which I believe, but just can’t get excited to have sex. She says she wants it back and I believe her—why else would she go through all this changing of the BC, the doctor visits, all that stuff? She tells me she feels awful and physically ill because she is so full of guilt. I hope I am not making her feel that way by expressing myself.
That is the story, but my question is, am I asking for too much? I love this girl so much and that is why I want to work this out. Honestly, if we were having sex like before, this girl would be my fiancée or wife today. This is the only thing holding me up. Is that a shallow thing to say? I love making love to this girl, I love satisfying her. I feel sex brings me closer to her. I know I am a good man to her. I respect her; I surprise her with flowers at work every couple months or cut one from the ones I grow and put them in her car before she leaves for work. I just wrote her a love note that I am going mail to her work, just to make it seem old fashioned and not the same like an email. But I need to know this can get better, because I do not think that I can live a full life like this. I would just not be happy. It hurts me to even ponder that really, but I think people should be selfish in matters like this and if they are not going to be happy, don’t even fake it.
Opinions from anyone would more than welcome, but I would like to know from ladies if I am being shallow and maybe if you have had anything similar with libido drop off and “recovery.” I don’t believe much in people falling out of physical attraction for one another if they are good to each other and not mentally or physically abusive or still keeping in decent shape and whatnot. Lack of commitment to working on things like this and being lazy, that is what I think happens.
