I think you should talk with your employer and see exactly what is expected, and talk with other fellow workers to see what they do. I had an internship a few years back that seemed somewhat similar. I would work in a desk for 8hours per day, no scheduled coffee breaks, and expected to eat my lunch at my desk. What I did was understand what my role was and what I had to do. I found out that as long as I met deadlines I would have some flexibility. I would bring a book (I love reading) and would take breaks every so often to do some reading. If it was nice out I would go for a walk. Because I always delivered quality work on time no one really complained about me doing this.

And guess what… Many other people did this. Even though there was no scheduled breaks, I found out that people would occasionaly go for walks and do stuff at work.

The truth of the matter is that a shift is happening in the work place. Longer hours and less pay is starting to become the norm. I would suggest you try to find some balance with your current work. Maybe negotiate over a few things. Realistically, they shouldn’t care as long as you are productive. And you are right… you need breaks to be productive.