Any possible diagnosis for constant fatigue, headaches, and dizziness? and frequent stomach aches? i have had loads of tests done but no diagnosis

Lots of things: Poor diet, deconditioning (out of shape), migraine disorders, sleep disorder, anxiety, depression, Lyme disease...the list is pretty extensive. I would gather together all the results of your tests, organize them by date and then keep a symptom diary for 1 month. Take all this information to a fresh set of eyes (maybe family medicine or internal medicine) to review.

Symptomatology: With all your problems and negative tests, I would recommend that you see a psychologist or psychotherapist for symptomsof depression or anxiety

Many Causes: There are many possibilities. Dehydration, low blood sugar, viral processes like mono, or sinus/ inner ear issues, stress, poor sleep, pregnancy, anemia, thyroid dysfunction, as well as tick-born diseases. All of which may cause headache. The list goes on. My thought in a healthy person with reportedly normal labs would be to ensure enough water, sleep and routine meals between now and follow-up.