A good question to raise. When you enter a relation, how much of yourself do you give? Where is the balance between altruism and pleasure?
I don't dwell on it too much any more: I honestly don't think there's a meaningful contradiction between the ideas of altruism, selfish pleasure, and loving someone.
Even the purest altruism, where you never think "I'll get laid if I'm nice to her", or "If I do him a favor, he'll be in a good mood and we'll have a lovely evening", but where you support your partner, help them at significant inconvenience, or continue to treat them well even if they've slighted you, may simply be acquiescence to a socially-constructed morality that you've internalized: you are kind because being kind makes you feel like a good lover, and thus validated (and when the pleasure of being validated as "good" is outweighed by the displeasure of the inconvenience, you stop being altruistic).
The point is, even if we try to, none of us can separate ourselves completely from our desires: it's in our nature as biological entities.
But then, so what? So what if they "only" love you because who you are makes them happy, and the intensity of their love of you will change if you change? Living in a state of constant change is a fundamental part of existing, and something everyone has to come to terms with.
No rational human would look upon a gorgeous gemstone, be pleased with it's cut, color and clarity, agree that it's a magnificent specimen... then scowl, unsatisfied, and say "Oh, but it's only a diamond because the carbon atoms are arranged in this way and not that."
TL;DR: Defining "love" only as disinterested, altruistic feelings is an extreme definition
And uh, I guess I love waxing philosophical.