Probably when all these things were happening you just got on with it and didn't have time to dwell on it or feel ( rightfully ) sorry for yourself. Now everything is just catching up with you and because things have slowed down you're starting to think about how terrible a time it was.
I read somewhere that a lot of people who work hard get ill at weekends or when they start their holidays because once they relax all the things they've been ignoring get a chance to creep up. Probably a similar sort of thing with you.
i know it's awful to feel like this but you're obviously not a failure because you have coped with all these difficult times, and you'll get through this too.
Talk to someone if you feel able, it will help and if you really feel it overwhelming you it might be worth a word with your GP. Try to find time to give yourself little treats - they don't have to be expensive, just little pleasures - buy a Wispa and eat it in the bath!
Hope you start to feel better soon. Take care. x