A lot of what you describe can just as easily be ascribed to ADHD as personality traits.

Have you been tested?

I want to make changes, I'm sick of being lazy, I'm sick of shocking people all the time with what I say because I never bother to think before opening my mouth, I'm sick of being lonely, I'm sick of postponing change.

This whole list is comprised of classic symptoms.

If not, or you're not interested in going down that road, I feel like I've been fairly successful at changing myself in general.

One of the methods I've used for this in the past, depending on the task, is setting up mini-experiments, sometimes in the moment, and then soliciting feedback. It keeps me pretty engaged.

Take your speaking without thinking example, next time that happens - if you have a close enough relationship with the recipients, ask them if they found what you said was shocking or odd, or if they felt it was normal. I've found the more often I can do this, the more mindful I become when the situations arises again in the future, and the easier it is to modify behavior and then solicit feedback again. The important thing to note here is that unless it is someone like a significant other's, a single person's feedback is irrelevant, but once you get enough of it you'll start seeing trends or patterns.

Over the course of time, using this and some other tricks and methods, I've been able to fairly substantially change how people view me; even those who've known me for a long time.

The final thing I'd throw out is to recommend you go a bit easier on yourself, and pace yourself a bit. Frustration with yourself is a good motivator, but wallowing in it too much is counter-productive and will make things worse, not better.