Annie, I feel your pain. When I first moved to SF I regularly got in to the office at 7am and I would work until at least 7pm. I often worked until 8pm, 10pm, midnight, and one time I was in the office until 4am. No joke.
But that's the way it is when you're just starting out in advertising or marketing or PR. The hours are brutal. The good news is that if you survive these early years, your salary will most likely go up exponentially in 10 years or so ... I know that is a long time away for you, but I promise you, it will happen. It worked for me!