Recommended lens for Nikon D3000?

[RebelsReadBooks]

I have been shooting using a Nikon 18-55mm lens and some of my photos have been distorted. I am aware this is due to the width of the lens and one way to fix this would be to shoot at no lower than 50-55mm. However, this isn't always possible, and I was wondering if there was a narrower lens with a shorter focal length available?
I apologise if this is a silly question. A-level Photography has taught me nothing.

 

[Phil Young]

You must be looking really hard to see distortion...can you post an example?

 

[RebelsReadBooks]

This isn't the best example, but you can see the vertical distortion gives it an almost fish-eye effect.

 

[Phil Young]

This isn't the best example, but you can see the vertical distortion gives it an almost fish-eye effect.

What's your exif details and how close were you?