Break up

I absolutely love this girl and I want to marry her. But its like we're either extremely good or extremely bad. It hurts that she might not love me as much as she used to. I don't want to lose her but I know its not healthy to hold on. I gave her my entire heart but it feels like its a one sided relationship. I cant with this anymore. I want her and I see myself marrying her but this last argument we had was just too much and pushed me too my limits. The last time we broke up, I became so depressed. So im scared of letting her go again. Should I break up with her?