I went to IU and applied this cycle (08-09) so I'll offer advice:
As stated above, don't switch your major. You are correct, undergrad majors don't matter. The only thing that matters is your overall GPA and your LSAT score. This is because those two factors are paramount when US News and World Report calculates their annual law school rankings. Law schools consider these rankings to be extremely important, so all other factors (whether you had a difficult undergrad major, or double major, or worked full-time during school, or was a captain of an athletic team, etc.) are considered "soft" factors and don't mean a great deal, except for tiebreakers.
I'd stop worrying about changing your major and instead work on getting a good LSAT score. Indiana's HPPLC department offers a really affordable LSAT course and you should get signed up for that. When I took it we met Tuesdays and Saturdays in Ballantine Hall for about three hours at a time for 6-8 weeks. I took the course twice and improved my diagnostic LSAT score considerably.