I think I'm gettingg worse?

I think I've been having depressive episodes sonce I was 9, but in recent years they are changing.

When I was younger I'd be sad in a constant way, but it was a lot more bearable. Nowadays I have very intense and very random episodes which leave me feeling utterly defenceless towards life, not wanting do to pretty much anything.

The main difference is that now I'm able to feel really happy again, even if only in certain moments, like while doing sports. And yet when it comes back it's like a punch in my face, bringing me down and stopping me from living normally, a lot worse than it did before, and I really dom't know if I can stand it.

I'm a different person than I was before. Learning about mental disorders made me realise that I mustn't listen to my self-destructing ways, and I now want to be better, healthier. And yet it's too much sometimes, too often, too soon. I'm tired of looking for ways to be normal, to get to a weight I desire, of never feeling enough for anything or anyone.

Having said this, what I would really like to understand is wether it is normal or not to have had such a random change in the way I perceive my episodes. I'd love to hear about other people's experiences, or even if anybody could suggest some book to read that might answer my questions :)