I believe I have an addition to Fast Food. Any advice?

I know this sounds stupid. But I have a hard time quitting fast food. I've gained a lot of weight, I feel awful most of the time, and I have no money at the end of the week. I am failing my fiance by pushing most financial responsibility onto her. I feel like a terrible person and I want to stop. But everytime I promise myself I'll stop, I always end up convincing myself I deserve fast food. Whether it's "I don't have time" or "I had a rough day" or "It's cheap". I know people go through worse addictions than this and I understand if this sounds like a non issue to most. But to me this has become a problem and I need some advice. I eat fast food at least once a day. Sometimes more. I fear for my health. I fear for my relationship. Thank you.