I don't have answers for you i'm afraid but idea's / opinions you are welcome to...

Did you ever have a collaring ceremony or some sort of similar ceremonial occasion? If so perhaps 'renewing your vows' might be a way to recommit to what you both want even the planning / writing of vows might help clarify exactly what feels missing?

Could it be that the time not playing but together is more important - service, comfort, little things that show submission rather than just the big one's - if missing out on these could be the issue maybe schedule some kind of 'date night' where hard play is off the table - to potentially connect better on an emotional level (though i don't think i would be able to stick to something like that - maybe there is a way to do it that could work for you)

Do you want to be re-broken on some level / in some way? If so why not do it - could be just the kick up the arse required...

Hope you find a way through this - 3 years is some achievement & best of luck for many more.