With all due respect, I really think it's worth getting a tick panel completed. Every time there are strange symptoms or things that don't make sense, I always think tick disease.
About ticks not being in your area, it doesn't matter. Shorty after I adopted Phoenix, I noticed that he became tired very easily. He couldn't even cross the street without resting. I finally found a vet who would send a blood sample out for testing, and sure enough he had a tick borne disease called babesia. The reason why I had so much difficulty finding a vet that would have him tested was because the offending tick (the brown tick) doesn't even live in Canada, which is where we live. Phoenix would have been infected sometime during his puppyhood or during his racing career. As Diane said, the disease can lay dormant for years. They can have a strange assortment of symptoms which often don't make sense.
These diseases can be fatal if untreated. I have no doubt that had I not had Phoenix tested and treated (with medication that had to be imported to Canada as it isn't available here), he would no longer be alive.