Confidence and Contribution

I try my hardest to contribute to the relationship. However I feel like I can’t contribute much other than paying for their food, spending time with them, and give them love. They go to a pretty good school and are pretty smart so they help me a lot as well as help me mentally yet I feel like I don’t deserve that love. As much as I work hard to contribute I feel like I’m not doing it right. They keep assuring me that it’s okay and that it’s fine, but it just doesn’t feel right and I keep apologizing and they get irritated. They’ve done so much for me yet I feel like im not worth it for him. I told them I’m working on being more confident yet I feel frustrated with myself for every failure or inconvenience I cause them. I’m not sure whether to keep trying even harder or to just be okay that I’m not on the same level as them.