This is a sort of by the way stemming from my earlier discussion of sexual infidelity.
One of the most compelling illusions in life is the illusion of sexual technique. That is the belief that what determines how good sex is for a woman is primarily a function of what you do for her. And these things are not irrelevant—a lazy, selfish or insensitive lover is a bad lover.
But the most significant indicator of how good a woman's sexual experiences will be is her ability to respond. She either can do it or she cannot and there isn't a sexual technique in the world that can change that. You might disappoint her but the upper limit of how good it can be is determined by her ability and willingness to respond to you.
And here is the brutal truth: If she can do it with you, she can do it with others. And she did do it with others! I know, no one wants to allow this but just accept it, the sex she had with others was probably just as good as the sex she had with you.
Yes, it is entirely possible that she is telling you the truth when she says it was never so good before you but probably not. She may even believe it herself because a break up will colour the way she sees things and she will look back and devalue the sex she had with the guy she used to love in retrospect.
The point here is, do yourself a favour and get over the notion that the quality of her sexual experience tells you how much she loves you. It doesn't. If you get abducted by Martians tomorrow who then hit her with a special energy beam that wipes your memory out of her head forever, she will meet someone new and have sex that is just as good or bad as she has with you.
If you want to know if she loves you, look to other criteria.
The other thing to remember is this: as brutal as this truth may be for men, it's worse for women. If a woman's sex life is unsatisfactory she may tell herself that it's because the guy in her life is a lazy, selfish or insensitive lover but she can only tell herself that for so long. If he clearly isn't lazy, selfish or insensitive out of bed, then he won't be those things in bed either and it is only active self denial that will maintain the illusion. And the degree of self denial mounts with every lover she has. We can do our part but ultimately it's her body and she has to figure out how to make it work (and not every woman succeeds).