I find that if I write things down I'll remember it better. It doesn't matter if it's on paper or computer, as long as I'm making the conscious effort to rewrite it instead of reading over it, I'll remember.
I applaud your enthusiasm for trying to solve a problem but there is no magic pill to get you open up around people. That may just be a part of your personality and why give people/girlfriend a false sense of who you are? Be yourself and words will form.
There is no medication for being nervous around certain people sorry