Interesting minor symptom of CFS - those who have a very clear memory of getting sick say they urinated a lot in the first few days of being ill. Anti-diuretic hormone being turned off. The Hopkins group has been vocal on this, and had some criticisms. They say you should eat salt to hold on to more water. If you have low blood volume and your BP is on the low side, they you should be safe to eat lots of salt.
Some patients crave salt.
Also try to drink lots of fluid. Some patients feel better from this, but usually only noticed in mild stages. Increase the plasma volume particularly. Astronauts have to helped out of the capsule - get orthostatic symptoms. A. Alcohol is very rarely enjoyed by ME sufferers.