Looks like you quickly got some solid feedback already. Don't be a victim of the pop, macho culture.
As Quilla said "Bottom line is, your ability to please women isn't tied to your penis." And as Blaidwynn pointed out - maybe it's a good incentive to learn and hone your other skills. Far too many guys go forth in life thinking that their tool is going to get them where they want to go. And end up wondering why their mates cheat on them or leave them.
And the advantages of a good relationship and poly is that you are talking, staying on the same page, and if the time comes that your GF(s) happen to be in the mood for a hard monster tool - well, those are a dime a dozen. You guys can find ways to fill that desire when the mood dictates.