Please help me become a better boyfriend

Just like the title said, I want to become a better boyfriend. Today me and my girlfriend had a huge argument, but not in a way you would expect. She just sat down I told me that she is really burn out from this relationship. She said that my actions and my words has left a huge scar on her heart. She said she wasn't feeling appreciate in this relationship, almost as if I had no feeling for her.

On my side of the story, I wasn't a guy that is observant, subtle. I had try countless attempt to make her feel loved, but the result unchanged. I do love her, and I love her a lot. We have so much love for each other, and don't want to quit this relationship at all.

I am writing this post out of desperation. I truly, REALLY, HONESTLY want to be more observant, to be that guy that is tactful and make their girlfriend feel love. Please, give me all your knowledge or learning sources, I am willing to learn. I will try everything it takes to become a better man, please help me out.