I've been demanding too much from my girlfriend
What were you demanding from her?
I was demanding that she loves me as much as I love her
It is ok to give ultimadums in relationships at times, however it may not be fair to force your partner to love you. Love is not something that can be forced, but is instead something that happens over time.
I don't think I'm expecting too much, love is an action and she needs to start doing something about it.
It's good that you feel so devoted to your girlfriend, but the fact is that this is how you feel.  She might not have the same level of feelings for you, and you shouldn't be trying to force her to have them.  If you want to do nice things for your girlfriend, do so out of your own love, not to try to get her to reciprocate.