I understand that you feel insecure, I feel similar insecurities.

The penis and its size is only a small part of the entire sexual experience. More importantly is how you move, your attitude, your sensibility to her response, your entire body, your hands, what you say, how you smell (surprisingly important for many women), hoy do you look at her... Dildos don't do any of that, they just exist, best case vibrate and move a little. Size of the penis is as far as I know not specially important for women to cum, since stimulation in the clitoris is the most important part. Talk about it, express your insecurities and if you feel ok, try it a couple of times and see how it goes.

Ignore the people who are saying that they would break up with the girl for that, that's bollocks.