I am sure she will feel it. If she loves you then even if she prefers a larger size, she will not tell you that. And you can both make it work.
Two inches would definately not do it for me.
Some women's g-spots are w a y up in there, but you don't have to hit it to achieve orgasm. It just makes the orgasm sooooo much better.
But, do not worry. Five inches is fine.
And no, masturbating will not shrink your penis.