Hi OP. I have many traits in common with you. Do you think your shyness is just superficial, or is it a visible trait that stems from something inside, something fundamental to you, something you intuitively feel is linked to your vulnerability?
I would really advise caution when entering a long term relationship with a person who wants to change you. Especially if she wants to change an aspect of you that is fundamental to your personality and your internal functioning, an area where you might be most vulnerable and need support and protection from a partner. This is where the long term partner would need to compensate for you. It is also the area where a wrong partner with a wrong attitude could hurt you the most and destroy your concept of self and your confidence completely.
I would suggest to pay very close attention to what Ovum said. Autistic Spectrum Disorder or Asperger's. Research the topic, at worst, you would learn something new. You might not be on the spectrum. If you are, it might be scary at first, but if you explore, it might help you to assert yourself. It might bring answers to the questions you were always asking in your head, but never out loud and give more power to you. It might give the key, the right approach to your growth and your confidence.
By all means explore various ways to grow and build your skills in areas where you feel you could grow. It will come with time and experience, as pictish described (I don't mean to say her DH is on the spectrum).
However try to differentiate between growing your ability to cope, and gaining acceptance by your partner of who you truly are. Because in the fundamental aspects of your personality, one cannot be a different person and one is not able to function at all if one can't be oneself.
I would also suggest keeping distance from and building a firewall against people with the attitude that Ginger and especially Aussie are articulating. They are treating social shyness as a deficiency in a person that has to be fixed for the person to be valid and acceptable to them as a partner. A person on the autistic spectrum, like me, experiences this attitude as discriminatory - I feel they would not consider me as valid and equal because of something so fundamental to whom I am, that I could not and should not change. It is a part of me that a true friend and spouse need to embrace fully and wholeheartedly.
When I was young, I could have been described in the same way as you describe yourself. The difference is, being a woman; I wasn't expected to take a lead in a relationship. However, often I felt the pressure to be an empathy goddess, socially charming, pre-empting and anticipating all the thoughts and feelings of the partner and to be all sorts of things I was not. I tried to keep up and grown from the experience. However it was in the context of a "taster" relationship, which I never felt likely to evolve into a life long commitment. For me it was trying and experimenting at low risk. I emerged stronger, more confident and emotionally scorched. I emerged with a resolution that for a real relationship, for a spouse I need a person that loves me for what I am, who would be "comfortable" for me, a "home front", and a safe protective person. Not a high maintenance person that I need to run after and win over everyday after coming home from stressful work. Intuitively I was deliberate in my search of a spouse that fitted me. I found such a person and we are in a long marriage.
May I suggest discussing possibility of ASD with you gf and see how she reacts?
Long time ago, I was dating a man for a short time, an IT wizard who was quirky and awkward socially. It didn't bother me because deep down I am like this too, but what put me off was his family - very protective and controlling. They pushed me out, and I was happy for that. But when many years later my DC was diagnosed with ASD and I understood the condition, I realised that that man was definitely an Aspie. His family were protecting him, but in a wrong way with a wrong result. I also realised I might be on the spectrum myself and this is why I was open and accepting of his quirkiness. He should have been upfront and open with me about Aspergers. It would have given our potential relationship a real chance. Now I know that he never married. He is still alone at 60.
My point is no matter how you feel now, you will find the right person too. However you might need to define your parameters and be deliberate in your search of a partner.