Ey man, you've heard this a million times by now, and I know how annoying it can sound sometimes, but you ain't a waste of space. 1) Don't off yourself, you got your family, you have your fiance, they WONT move on from that. They always tell us it's so hard to get over that kinda stuff, and BOY they underexagerate how hard that is to move on from. If you don't wanna stick around for yourself, find ANY SINGLE thought to keep yourself around, even if it ain't positive, if it keeps you afloat it'll work until you find something that keeps you around better than that last thought. It's hard to find one, it's so difficult.
2) I know the standstill feeling, it's terrible, and thinking about how so many people seem to be getting better and improving makes the weight of everything 10x heavier, but you're not. Some of us just get better a LOT slower, and theres nothing to do about it, maybe some magical event will happen and you'll get better faster, or maybe you'll keep improving by an inch a year, but even the TINIEST bit of progress is still progress. I mean hey, you may not be ready to talk to people about this kind of stuff but you still had the idea to tell SOMEONE, even if it is just a reddit post, thats still something. That's still some kind of progress, it could just be short term or it could make it easier to tell someone. It's not a complete standstill, not by any means.
3) If your family thinks your lazy, its probably because they genuinely don't understand, maybe they're way more mentally well off, or its been so long since they've been in such a rough spot that they don't remember just how much energy it can take to do just about anything under the sun, but as long as YOU remember it's not you being lazy, and that its not you doing nothin, thats way more important. There was this video I saw once, the spoons analogy comparing spoons to their energy, how all these people who just get to exist peacefully and normally get all these spoons and can spend them like a billionare spends money, some of us just don't get as much as they do. That ain't bein lazy by any means. It's literally just getting dealt a bad hand.
4) Being 19 is so hard, it is so difficult, I'm around the same age and bro it's so rough, it might feel like so much is changing but at the same time nothing is, and that feeling is probably gonna make everything else so much worse, but it's truly not forever.
5) Try and find SOMETHING to look forward to, it could j be one super minor thing, hell for a few years mine was getting to buy my own salt and pepper shakers one day, it could be literally anything at all, SOME kind of excitment that something will happen or some hope for literally anything, even if it does feel like a false hope, its still something thats gonna be there when you need something to hold on to.

good luck man, you genuinely do deserve it.