http://www.bodyandsoul.com.au/sex+da...+normalr,25351
One main point mentioned
"The size or shape of your penis isn’t the most important factor in pleasuring your girlfriend. The vagina is what is called a “potential space”. This means is stretches to accommodate what is placed inside it. It will snugly wrap around whatever size you are, and it’s the motion that will stimulate her physically. What’s more, the pleasurable nerves are only located on the outer one third of the vagina – any deeper and she’s not feeling it anyway! And even more:
the average vagina is only 4 inches long to begin with. Many women report men who are too long can actually feel uncomfortable or even painful. More still: the most nerve endings – eight thousand of them – are not even inside the vagina – they are in the clitoris, which is where you want to be spending more of your attention!
Remember: whether your willy is a weenie or a wowza, it’s all about how you work it!"
So if your 4 inches .. your still ok