Ever hear of the Seven Year Itch? Sounds like you've got it. There is a term for "getting bored with someone you're used to, and taking them for granted." I saw it in a Cosmo magazine. Forget what it is right now.
Unfortunately I see my gf having that feeling towards me, and we've been together only 4 years, and she's had it for a while. We were crazy sexual when we first met, did all this kinky stuff, sex every day, for hours. Now, sex maybe twice a week, perfunctory, maintenance style sex. If I don't initiate it doesnt happen.
However, I was in a 30 year marriage previous to this one. I can attest that sex can become boring, stale and infrequent, but then, through some kinds of life changes, can become extremely hot and honeymoonish again!
In my case it was just maturity. Knowing myself and what my turn ons really were, and my ex-h becoming aware of, and accepting and celebrating my turn ons so much, they became huge turn ons for him as well. And encouraged him to try different things he liked, which I embraced. We went from a point to where we were only having sex once every 4-6 weeks, to sex 1-5 times a day!
Back to my gf... we have lots of romance and cuddling and kissing... and she is diagnosed with anxiety disorder which does interfere with her libido. It waxes and wanes. Sometimes she does rally and we might have some pretty hot sex 3 days in a row. I don't take it personally... or I try not to. Sometimes she seems to feel because I have a horny bf for my needs she is off the hook to have sex with me! No. That is just silly. I desire HER, even if I am getting it from Ginger.
I do think it's sad you don't want to give your gf oral anymore.
Sorry to sound sexist, but, this is why women have learned to play hard to get. Men love the thrill of the hunt more than actually eating the prey.