girlfriend is ashamed of me

so ive been dating this woman for almost a year now and i felt like i did every thing right at the beginning of our relationship i wrote her poetry, love letter, we would take long walks on the beach, the whole thing, and then i started to let myself go.: gain weight, didnt care how i looked. and now she has admitted that she is ashamed of me. she never said anything bad to me about it but i over heard her talking to her sister about me in which she said how she is ashamed of dating me and how i let myself go. i dont no what to think now. im feeling that i need to break up with her. i want to loose weight but i also dont want to change who i am for somebody else. we planned to buy a house and get married together and now i want nothing to do with it. im just so confused. i dont now if i should keep trying.: