My gf my penis is very small ..she can't feel it ...It got me little worried ...is it small?
Your penis looks at least as big as normal.
If your girlfriend has experience with other men before you, I can't question her experience. I'm sure she knows what she feels and doesn't feel. However.....
Lots of couples don't realise that the inside of the vagina is nothing like as sensitive to stimulus as the outside of the penis. Some women never have vaginal orgasms, which means they need a lot more clitoral stimulation to reach orgasm. My wife and I used to have plenty of foreplay and usually she achieved orgasm with stimulus with my fingers. We would get there before I entered her. Another big difference (typically) between male and female is that stimulus after orgasm can be unpleasant for males but fine for females. However, we are of course all different too.
I'm wondering what she thought would happen after she told you? There's not much you can do safely about your penis size, but she may be able to exercise her internal (Kegel) muscles so she can grip you better. If you care for each other genuinely I'm sure you can find ways to make sure both of you have satisfaction.
It looks a normal size to me, and size isn't as big a deal as most men seem to think anyway. How old are you, and how long have you been with your girlfriend? How many partners have you had, and how many do you think she might have had?
If you google "penis size NHS", there's a very good article.
Thank you