Lab results for blood may be good, but those are not the only indicators of health. You may want to consult your doctor for additional diagnostics. Frequent headaches are never a good sign of anything. If you fell when you passed out, it could be the effects of a concussion. A CT Scan or MRI may be needed. Not a doctor, but generally speaking, sudden onset stuttering comes as a result of an outside influence or environmental factor. Yours may be your passing out, and potentially be a brain injury.