Sometimes people feel uncomfortable when there are big differences between them. This is especially true among teenagers, like yourself, who are super sensitive to fitting in with peers and groups. That said, your boyfriend probably likes that you are honest about your modest means, and that you are industrious in that you have a job. I’m sure he loves that you are thoughtful and buy him gifts at Christmas and other such holidays, but you need to ease up and understand that just as you are not responsible for your family’s modest means, neither is he for his family’s wealth.
Let him buy you things and pay for things, and you continue to buy what you can afford for him when it’s his birthday, on Valentine’s Day and other holidays. If you feel guilty about his spending his money on you, rather than fight about it on a date, you can offer to pack a picnic lunch for a park or beach date, or you can bake him cookies or do other things that are thoughtful and within your means.
The most important thing in your relationship is your feelings and the way you treat each other. It sounds like your differences are only financial, and if you can accept the disparity, and be gracious and honest, I don’t think there’s a problem with his being generous, as you’ve described.