I am unsure about the relationship i'm in. i love him, but i'm not ever really happy anymore. help!?

i am engaged and have been for a few months. i thought that i was going to be ecstatic, but i have found that i'm not. i often pick little fights and i am driving myself crazy. if i want to be with him so badly, then why am i sabotaging my own relationship with the only person i could ever see myself with? what's wrong with me? ...