You are speaking about being "in love" as if it it some religious truth. I believe that love is different for each person. We all have our own ideas needs and desires.
I also think you are confusing love with sex. They aren't the same thing, there are friends I love deeply for whom I have zero sexual desire, and there are people I would jump into bed with in an instant. Although I may have affection for them, I cant say I love them in any idealized sense.
People enter all kinds of sexual relationships. If you want a transcendent experience where you lose self to enter the astral confluence... I wont judge (although I am skeptical). I certainly dont want this.
For me the best sexual relationship is honest and down to earth. Each person gives what they have and gets what they need.
In your hypothetical, communication still works. If you need something that I cant give you, lets be honest. Not every sexual relationship is meant to be. If it is not good for both of us, I would prefer to be honest and end it.