Fatigue, joint pain, occasional red rash on face, positive ANA (twice), C3 is 73 and C4is 14. Could it be lupus?

Maybe. The real question is "Should we TREAT you for lupus with godawful high-power medications when you probably don't have it?" People with a clinical picture like yours usually have all this stuff go away after a while. Get seen by a specialty dermatologist for the rash; rosacea can mimic lupus. Ignore low-titer ANA's. Think about getting back to that fitness-focused lifestyle you had as a teen.
Probable. The diagnosis of SLE is based on clinical features plus supportive lab evidence. You did not mention how high the ANA titer was and thus a positive one has little meaning. I believe you need to see a rheumatologist given all of your symptoms which may well be from SLE but....