Re: Tips to increase energy and endurance?
Besides the very good advice already given, I'd note that one month is a very short period of time. The symptoms you're experiencing right now are simply telling you that your current conditioning level, combined with nutrition and recovery, is not adequate for what you are trying to do. You're more likely to have long-term success if you take a systematic, progressive approach to conditioning. This will probably require at least temporarily backing off some of the time you're giving to the activities you enjoy, and giving that time instead to conditioning activities or rest.
Walter has given good advice on nutrition, to which I would add that the secret to healthy eating on a budget is to cook it yourself. One of the great modern tragedies in the USA is the ready availability of "food" that is cheap and convenient, but very nutrient-poor -- for example, the "value menu" at fast food restaurants. A pot of beans and brown rice and vegetables is even cheaper, but it takes more work and doesn't taste as good (to people whose tastes have been conditioned to like processed food and lots of meat and salt). I heard someone say recently, "You gotta be wealthy to eat healthy," and it's just not true. You do have to be wealthy to eat a diet that is really varied, contains lots of meat, and is effortless and extremely convenient -- but that's asking for a lot. Within a grad student budget, you can purchase and cook food that's excellent fuel for a very active person.