My turn to change things

Hello. My first week of PM is almost finished. The first few days were not a problem, but today I'm struggling a bit.
Why I decided to enter this challenge is because my girlfriend and I started to have sex less and less frequently. It happens once or twice a month. We are both 24 in a 4 year long relationship that started very romantic, but now we are like a really good friends. We had a lot of sex before, we experimented in bed until we found out how to best pleasure each other.
We had a conversation about that and she knows that I want us to have sex more often. But some time has passed since and things didn't change much. I went through phase of blaming myself for not performing better in bed, for not being attractive enough, but I realised it's a lot complicated than that. I stopped thinking what I did wrong and started to work on how to become someone better.
To improve I need more motivation and I think this is the first step to keep my focus on things I want in life and that is to study harder and find other activities in life that can make me more interesting person. I used to caught myself lying, resting in bed for hours playing games on my phone, visiting porn sites, masturbating out of boredom and then get back to playing games because I had no willpower to go study.
So I'm actually doing this for me and her, to last longer in bed so she can have orgasm every time we have sex, to become more successful man so when she looks at me she sees someone whom she wants to drag in bed.