I haven't got time to be tired!

I'm so tired.
And I've come to realise that I'm always tired I've just been ignoring it. It struck me couple weeks back. It was my birthday (did I say that I turned 40 on the 3rd March?) and Craig and I had a day out. My parents picked Seth up from school and kept him overnight so we had all day and night. All we did was jump on the train to Milton Keynes, mooch around and go to the cinema but it felt like a complete holiday from my life. I felt free. We then travelled back to Northampton and met up with friends in the pub. It was a perfect day.
But every since then I've realised how tired I feel normally. I think going to the gym regularly has saved me because it makes me feel so good and energised afterwards but I'm definitely craving sugar more. So much so that I actually took fruit into work yesterday to try to get some healthy sugar in me and I was actually still feeling hungry whilst eating some strawberries! I'm not a fan of fruit! I'm certainly doing a lot more - I'm actually regularly tidying the house and studying, plus planning to start doing massages again which on the face of it might seem a daft thing to do. But I was tired before when all I did was sit on the sofa watching telly at every opportunity and then I just felt shit because all I did was sit on the sofa. Now I might be tired but also feel that I'm accomplishing some stuff. And it isn't any of that stuff that makes me tired - caring for Seth makes me tired. The rest is me trying to find stuff that makes me feel good. The most stupid thing that I do is try to get more responsibility at work. I should just keep my head down and just take the money. But I can't bear the thought that people don't think I'm up to it. But maybe I'm not! Maybe I really don't have enough left in me to take on any more and should be happy that I've got a job that I mostly enjoy and with people that I love working with.
But its not just about being tired. It's the emotional down that comes with it. Caring for Seth, even when he is at his loveliest, is still a drain. I think he might be having little fits again- little brain spasms which have only the subtlest of physical 'tell'. & the last 2 Sundays he's definitely had some kind of fit, again really small signs but the way he has zonked out afterwards confirm my suspicion. I know I should tell his consultant but all we'll do is have another eeg which will either show something happening at that particular moment, or not. He'll talk at me for a while and then we'll carry on as we were.