I live a healthy and active lifestyle, but the last few months i've been feeling tired, light headed and almost like i'm in a dream. what could it be?

Unfortunately there: are so many possible causes for your symptoms that it will be nearly impossible to diagnose you accurately over the internet. You need a physical exam and laboratory testing as well as a thorough history evaluation to determine the cause. Make an appointment to see an Internist soon.

Need to examine: It is not feasible to provide a meaningful opinion without taking additional history, physical examination and may be some tests. It would be prudent to see your doctor and discuss if you may be depressed. 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.

Labs needed: There can be many causes most common being Anemia,Thyroid problems.Fatigue is a symptom of many diseases.Needs good physical exam and lab work.

Dream-like state: In addition to Dr. Ira's excellent answer that there are many possibilities and your need to see a doctor consider this please. If no physical cause is found, a clinical psychologist may be helpful. Your situation may be stress-related and we can subconsciously protect ourselves. Also, fatigue can be a symptom of depression. Peace and good health.