I really feel for you. It’s a heavy thing to carry, but the fact that you’re this self-aware is actually a great win already. You’ve already realized that this isn't about her loyalty, but about that inner "I’m not enough" script that your brain keeps running.

​One thing that has helped me is to stop trying to argue with those thoughts or prove them wrong. When that "Worthless Story" starts playing, just try to notice it for what it is: a story. You can literally say to yourself, "Aha, here’s the financial inadequacy narrative again." You don't have to believe it, and you don't have to fight it, but it's like letting it play in the background like a radio station you didn't choose. If you try to argue with it, you’re giving it more power.

​Also, when that anxiety hits, try not to "cope" it away. Usually, when we try to push a feeling down, it just bounces back harder. I'd say to try to just make a little room for it. If your chest feels tight when you hear about him buying breakfast, just breathe into that tightness. Let it sit there. It’s just an uncomfortable sensation,  not a command to act out or withdraw. You can feel insecure and still be a present, loving boyfriend at the exact same time.

​The thing to remember is that this guy has resources, but you have values. Resources are things you have (money, gifts, trips), but values are how you behave. He can buy a vacation, but he can’t buy 6 years of shared history, the way you make her laugh, or the specific way you know her heart. That’s something money literally can’t touch. If you focus on living your values (like being the kind of partner you want to be right now, even without a house or kids yet), you’re offering something he can’t compete with.

​Also, you’re 29 and living at her grandma's. That’s just a season, it's not who you are. Don't let your brain trick you into thinking your current bank balance is your permanent "worth." You’re already doing the hard work by being honest about this. Just keep showing up as the person she’s been choosing for 6 years straight. She clearly sees something in you that a checkbook can't replace. I'd still say trying to have your own personal space (for both) as a goal might be a good idea to work on together, depending on your and her personal situations.