Even though there is a difference between being sleepy and being fatigued, a lack of sleep can be one of the reasons for fatigue. A sleeping disorder like sleep apnea could be the reason why you're feeling tired all the time. During sleep apnea, a person will stop breathing for a few seconds to a few minutes. They will suddenly start breathing again after a loud snort or choke. This pause in breathing occurs somewhere between 5 and 30 times an hour. When this pause in breathing occurs the person will go from deep sleep to light sleep and won't get the required amount of deep sleep.