I feel constantly tired, ache, depressed. Have an underactive thyroid, but on 125 mg Levothyroxine and blood tests for that all normal. I have one day where I feel alive, energetic, then it gets replaced by total lethargy, tearfulness and struggle to do anything. My sex drive has become non existent too. I am 40 years old, weigh 9 st 5 ( but weight keeps piling on despite exercise and sensible diet) and I cannot stand to feel like this.