31M 4 F Looking for someone to talk to

Recently I had a breakup with my ex which has been 3 years, the reason she told me that it was because of lack of deep connection with me throughout the relationship and it hurt me so much because there's no communication or discussion bout this issue before. Weeks later, our friends in common told me that she's seeing someone and she tell them that she's into him because he can provides what I couldn't.

I really wanna know what's the true reason behind it and how to be a better person so that I won't have to face the same situation again in the future.