I feel like i am fighting a fever but have no temperature. this happens often and ive never been given an answer but it really knocks me down when it happens. any ideas?

Some definitions: everything and one has a temperature even when dead. A fever is a temperature that is above normal for you. Everyone seems to have their own temperature set point so what is high is one may not be in another. So define what you mean by fighting a fever better.

It is not feasible to provide an opinion without additional history, physical examination may be some tests. It would be prudent to see your doctor to see if you may be depressed. Depression is treatable. Counter-intuitive as it may seem, exercise may help. Start with low intensity exercise such as walking and gradually increase the intensity as tolerated. Drink more water. Wish you good health!