Fixed lens for Nikon D3100?

Right now I own a fixed 35mm Lens, but lately I've been a little unhappy. I feel like the only way to get a great depth of field with my lens is to be relatively close to my subject. I was curious if I could get a better depth of field with a 50mm lens. Say I was taking a picture of a person, and I wanted ankles to the head in my picture, would I be able to get a better depth of field with a 50mm than with a 35mm. Would you suggest that I just save for a 50mm 1.4?

Added (1). Yes and I do know what depth of field is for those of you who don't know what being rude means.

First a little less in terms

A fixed lens is one that can't be removed from the camera

You fine D3100 uses interchangeable lenses

That means that your 35 mm lens is NOT a fixed lens.

Single focal length lenses are called "prime" lenses as opposed to zoom lenses that have multiple focal lengths

Next a 50 mm lens has less depth of field a a given lens aperture, so the 50 mm will actually do the opposite of what you want. The is true for every lens. The longer the lens, the shallower the depth of field at any specific lens that is shorter

Do you have the 18-55 mm lens? If so, just set it at 50 mm and tape it there. Then use it for a full week at 50 mm. You will learn a lot by doing that.

What does that mean? Well, you can set your kit zoom lens to 18 and again tape it there and use it too for a week.

As you will see, the shorter the lens, the more apparent depth of field

Fixed lens means unremovable. Your camera has an interchangeable lens mount. To make the lens fixed, try gluing it to the mount. What you meant is a fixed focal length lens or prime lens, the ones that don't zoom.

Great depth of field means everything is in focus. If you want to blur background, you are after a shallow or short depth of field (DOF).

http://keerok-photography.blogspot.com/2011/05/how-to-blur-background.html

You can get the whole person, from toes to the top of the head, if you move that person as far away from the background as possible with you as near as possible (with the subject visible from head to toe) while using the lowest f/number on your 35mm lens. It would help a lot if there were lots of light around the subject.

http://keerok-photography.blogspot.com/2011/05/lenses-so-many-of-them-there-is-no-best.html

Getting a 50mm lens will just change the angle of view. If your 35mm is f/1.8 and you get a 50mm f/1.4, you will be able to blur backgrounds much more easily with the 50mm at f/1.4.

You clearly have no idea what "depth of field" means.

For portrait 85mm would be better than 50mm.
Having said that, adding a 50mm to your kit is not a bad idea, since 50mm/1.8 is relatively cheap and from there save for 85mm.