Any advice please?😩

Im a guy, I decided to get this app because I know women out here give good advice too . I cheated on my girlfriend before and now we're back together after 3 months of being separated.She overthinks a lot, she feels like she's not good enough for me and doesn't trust me a lot because of what I did. She doesn't want to get Hurt again but I really don't wanna hurt her. I love her so much and it took time for me to finally realize it. She has all my passwords and has access to my phone. What can I do to help her stop overthinking, I hate when she feels sad about everything and it makes me feel like shit because it's all my fault.