So when I start dating someone new she is always eager to please me in bed. She is very concerned about the fact if I am having a good time with them in bed. But over time she stops giving a fuck and sometimes even deny sex by just saying she's sleepy or tired. She also talks to me in a tone as to emphasize that I am a bad person if I think sex is extremely important to the relationship. She insists connection is more important. What might be the reason for such behaviour? Is it something I am doing?