So, lesbian bed death is definitely a thing. Help!

I've been with my fiancée for almost 2 1/2 years now. We are in a long distance relationship at the moment as we live 500 miles apart, but we visit each other every 6 weeks or so as work permits (we both work full-time). That has it's own challenges but we make it work and are very much in love and making plans to close the distance soon. All of that is beside the point but I wanted to give some background info first!

When we first got together, our sex life was great, like most couples, I'm sure. Whenever we would visit each other, we couldn't keep our hands off each other and were having sex at least once a day for quite awhile. I don't expect things to stay that way - I know things tend to calm down once you've been in a relationship for awhile. But I'd say for the past year or so, things have really died down. So we see each other about every 6 weeks, like I said. Usually, it's me traveling to visit her, since she doesn't have her license, and that's fine really, I don't mind that. During that time we usually get to spend 2-3 days together. For quite awhile now, I'm noticing that she very rarely initiates sex - I'm almost always the one who does it. And when I do initiate it, I'd say 70% of the time she will say she's not in the mood/just wants to cuddle/something of that nature.

I really feel like crap even feeling this way, because I'm certainly not going to ask her to have sex with me at a time when she doesn't want to or pressure her to say yes - and I don't. I accept her answer but lately it's becoming an ongoing thing and I have brought up to her my last couple visits that it hurts me and honestly it feels like she doesn't want me physically/sexually anymore. She insists this is not the case and that I just have a higher sex drive than her, which may be true, but keep in mind I'm not trying to have sex with her multiple times a day. I'm there for 2-3 days and usually a day or so will pass and we haven't had sex yet, so I'll initiate and she'll give me a reason or tell me it has to wait till later.

Then when we do have sex, it feels like I'm the one putting forth all the effort. I do all of the things I know drive her crazy, because I want to and I enjoy it. But when she touches me, it feels like minimal effort -- same position, same routine, no talking on her part... and things never used to be like that at all.

She's aware of how I feel and at the end of our last visit said that we will work on it, but I have my doubts considering she's said that before in our last couple visits. It's not a matter of top/bottom either - before things calmed down, she was actually more of the top, but we both put in an equal amount of effort. Now, it feels like I'm the only one who cares about our sex life and any time I initiate sex I feel like I'm begging her or asking her to do something she doesn't want to do. It sucks and I'm kind of at a loss here on what to do.

Does anyone else have experience with this? I seriously will take any advice I can get. I love her with all of my heart and want to spend the rest of my life with her, but something has got to change because I'm going crazy over here.