I'm a bit late to the topic, so quite possibly you've moved on, but

> I keep failing and getting frustrated as soon as I hit a wall, I didn't used to be like this but now everything seems too hard

> depressed and demotivated

Just one of many possibilities, but you could have a neurological disorder ("I didn't used to be like this" and depression, no motivation). Go to a decent doctor and get checked for a bunch of things. Could be something treatable like vitamin deficiency.

In any case, feel free to ping me, emails in my profile.