When did I get so old?

One day I was 23 and the next I am over 40! When did that happen? I feel old today, I guess that is why I am thinking about it. Most of the time I don't. Partly because I am so tired, I am exhausted if I am honest, but yet I can't sleep at night. I go to bed and can't get to sleep, then when I do fall asleep I wake up a few short hours later. Then I lie awake for about an hour or sometimes more, until I doze off again. But I don't seem to sleep for the 7 or 8 hours that I need. Unbroken sleep. So I am tired. I am also feeling physically tired, probably because I am not doing anything, just sitting here in front of the computer playing bejeweled, checking email and surfing the net. I don't get much if any exercise, other then running up and down the basement stairs to do laundry. But I can't afford the gym, and it is too cold to get exercise outside. But why do I wake up feeling exhausted? And why do I go to bed feeling like I have been run down by a truck every night? You know that, all-over-body tired feeling? I suppose I will get fit again once I can get to the gym, and for now will just have to get used to being too tired to be bothered to do anything. Until I get to go to work again, which fingers crossed will be soon.