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You sound heartbroken and in a lot of pain. Since you asked multiple questions, I will try to address each of them.
With respect to your girlfriend, you have already tried to reach out to her in several ways that have been met with some pretty firm resistance. I would say that you could try writing her a long letter expressing your feelings (a letter allows her to read it over on her own time and maybe multiple times if she'd like).
You might also suggest that you'd be willing to go to see a couples counselor together if she would like to so that you could be on the same page about what's going on- how your relationship went until the break-up, what the break-up has been like, what she would need from you in order to get back together, what you would need from her, and/or how to break-up with the least amount of pain possible if breaking up is the only option left.
You could also try going to individual therapy to work on some of your own parts of this. For example, you mentioned that you are not very verbally expressive. There is nothing inherently wrong with this, but it has (and could in the future) posed problems for your partner- so working on how to express your feelings verbally and be more comfortable with this might be useful to you in several ways. Individual therapy could also be helpful in giving you the support you need to take care of yourself without your girlfriend around (even if she "comes back", this is useful).
Ultimately, I think that once you have expressed yourself in all the ways above (in addition to the ones you've mentioned), there is nothing more you can do to convince your girlfriend that this relationship is right for her- and continuing to try might just feel like harrassment to her.