The problem you have, in my opinion is not necessary to have a wider lens, but first to learn to use what you have.

1) Learn to use the zoom lens you already have. The other users already told you that you probably have a 18-55mm lens. Move the big barrel.

@inkista it does provide a wider frame. I just don't like to use the 18-55 indoors (unless I'm doing something - which is quite possible)

2) This soudns that you have a low light situation. Change the ISO to 400 indoors. Try ISO 800, change your aperture to max aperture. Turn the Image stabilizer on. Also try to use a tripod.

3) If the thing you do not like is that you need to use your pop up flash, buy an external flash, with a remote controller (there are combos really cheap) and learn to use ambient light + a flash bounced to the ceiling or a wall.

4) Have you tried turning your camera 90° (portrait) to fit what you need?

5) Define why you do not like to use the zoom lens. I hope it is not the distortion on proportions.

6) If everithing above fails. Just then you probably need a wider lens.

Go to a store with your camera and ask to see some lenses arround 10-20mm like this one: http://www.sigmaphoto.com/10-20mm-f4-56-ex-dc-hsm (just an example)

You will notice that the numbers overlap a bit with your 18-55 (10-19-20)

Go phisically to a store to see in person the effect of that kind lenses, try to shoot the salesman and see the distortion vs. your space so you can calculate your house proportions.

Look to buy one of thoose after you learn how to use your kit lens.

7) Shoot outside.

With the problem you have, in my opinion, it's not necessary to use a wider lens, but first to learn to use what you have.

1) Learn to use the zoom lens you already have. The other users already told you that you probably have a 18-55mm lens. Move the big barrel.

@inkista it does provide a wider frame. I just don't like to use the 18-55 indoors (unless I'm doing something - which is quite possible)

2) This sounds like you have a low light situation. Change the ISO to 400 indoors. Try ISO 800, change your aperture to max aperture. Turn the Image stabilizer on. Also try to use a tripod.

3) If the thing you do not like is that you need to use your pop up flash, buy an external flash, with a remote controller (there are combos really cheap) and learn to use ambient light + a flash bounced to the ceiling or a wall.

4) Have you tried turning your camera 90° (portrait) to fit what you need?

5) Define why you do not like to use the zoom lens. I hope it is not the distortion on proportions.

6) Only if everything listed above fails, then you probably need a wider lens.

Go to a store with your camera and ask to see some lenses around 10-20mm like this one: http://www.sigmaphoto.com/10-20mm-f4-56-ex-dc-hsm (just an example).

You will notice that the numbers overlap a bit with your 18-55 (10-19-20)

Go physically to a store to see in person the effect of that kind lenses, try to shoot the salesman and see the distortion vs. your space so you can calculate your house proportions.

Look to buy one of those ultrawide zooms after you learn how to use your kit lens.

7) Shoot outside.