I think you don't quite understand the story. I was not being used, because I didn't allow her to use me.
Often she tried to initiate sex after I did something nice for her. But sometimes she acted like she was doing me a favor by having sex with me, all those times I broke it off. Sometimes I knew that she wanted it at the moment, and she sincerely wanted it, but I didn't like her acting like she is doing me a favor.
The situation I described wasn't something that happened every day, it happened about 4 or 5 times in a period of 8 months.
I'll give an example: She knew about a secret that I have, but she didn't know the secret yet. She promised me a bj, in return for te secret. I declined. A week later I told her the secret anyway, she initiated sex, also here I declined. Because, if we had sex at that moment, it would feel like she had me by the balls, and not in a good way.
The reason we stopped having sex regularly has nothing to do with this and is an entire different story, I shouldn't have brought it up, sorry to be confusing.