Hi Neferata, it's really hard when your sexuality is bursting out of the gate after years of repressing it, because it feels like there's so much at stake. The feelings are so intense, when it works it's the best feeling in the world, and when it doesn't work, you feel like everything has been ripped away from you.
It's like the tide though, it comes and goes. Those feelings will return, and you will experience them with many different people you meet in the future. There's a big difference between two people having different sexual or relationship needs, and your entire sexuality being inadequate. Her desires are her own, and your desires are yours, and they are equally as important.
I don't know if what I'm about to say matches with you, it's from my own experience. That inadequacy you're feeling comes from being different and not fitting in. It can make you so desperate to be loved and be intimate that when you meet someone who's interested in you, you throw all your own needs out the window and only focus on theirs. You describe yourself as 'selfless' so it sounds like this is already part of your personality.
Boundaries are so important, and it sounds like you have a great relationship with this person, but maybe it might be better as a friend? You'll need good friends alongside you as you carry on this voyage of discovery. It's an exciting time, even though those crushing weights can dangle overhead as you go. :)