We've had a number of threads involving similar situations. As I've often said, many women have a very pragmatic view of diapers. Having their partner wear them - for whatever reason - often doesn't seem to rankle initially, but their discomfort increases as time goes by This is because all the conditioning they've received over past decades 'kicks in' over time.
I think there are three paths for you: First, you can offer to give up diapers altogether. This certainly seems unreasonable to me, but I have a partner who actively participates in my AB lifestyle. However, your Significant Other may require this if you are to continue the relationship. Be forewarned that giving up diapers altogether is difficult at best and probably impossible; you'll need to prepare yourself for the emotional longing and discomfort you'll encounter with such a bold move.
Another way forward might be to have a lengthy dialogue with her focusing on why she suddenly isn't comfortable. Be aware that this sort of conversation may provoke anger or frustration because, due to their conditioning, many women cannot understand why a grown male would have an attraction to or need for something they think suitable only for a baby.
The other option is to agree that you won't give up diapers, that she will continue to be increasingly uncomfortable with them, and that you're giving up your relationship and moving on as a result. I frankly think this is preferable to having to lie to her or resort to the various forms of subterfuge we often see brought up here. Moving on might also be a viable alternative to the anger and resentment involved in attempting any sort of 'compromise' related to your diaper desires. Most of the time, compromises just fail to satisfy one party or the other, and a breakup is the end result.
I wish I had more positive thoughts for you. The simple fact is this: None of us asked to be born with these desires; I, for one, certainly wish I could outgrow them. Having failed to do that, however, I'm left with finding an accepting partner or being alone. Accepting partners aren't exactly common, but they can be found. Perhaps you ought to begin the search sooner rather than later.