how can i be more myself??

I feel like i’ve tried so hard to be the best gf my bf has ever had and in that, been trying to be something i’m not. I found myself comparing myself to his ex gf and trying to be better than her and i’m just so exhausted. i’m a great person myself!! I wish I can be more forward in showing that. I used to be so carefree when I was younger, does anyone have any advice to just let lose and have fun? I feel like i’ve grown to be so uptight.