Have no fear.
One of the most exciting aspects of the design field is its diversity. Since talent and creativity are the fundamentals for any designer, a major in English, philosophy, business, or even engineering isn't necessarily shut out. In fact, having a degree in something other than design makes you more marketable towards future employers.
If you are currently in college, the first thing you should be doing is research. Find out exactly where you see yourself and what you have to do to get from point A to point B. If you can, take any design-related courses you can. Even if they aren't applicable for your major, any practice will put you ahead in the long run.
One of the most important things any budding designer must do is practice his or her craft. Practice as often as you possibly can, for pleasure or for fun. Instead of turning in a project in "Times New Roman" font, for example, do what you can to make it design-conscious. Some teachers won't like this, but most will notice the extra effort.
In your spare time ("What spare time?" you might ask), read design publications, books, and websites. Keep up on the industry in every way you can.
Although potential employers appreciate diversity, they also want to see that you can handle the design challenges they will throw at you. You will still need to present a portfolio, as well as assuring you can use design software.
Unfortunately, it is becoming increasingly difficult to have a competitive edge without some sort of formal design training. You may be able to break into the field without design education, but unless you have a stellar portfolio and solid computer training, you will not be worth as much as you peers directly out of college.
In order to gain this competitive edge, there are graduate-level programs that do not require a portfolio for admission. Portfolio Schools, as they are called, accept students from many educational backgrounds, often finding students with various degrees more appealing than those with design degrees.
The ultimate goal of these programs is to prepare students for the design industry by preparing their portfolios. Since portfolios are the ultimate ticket to design success, they are the foundation of the two-year program. Every assignment is geared toward giving the student the most well-rounded and impressive portfolio possible.
While these schools do not require a degree for admission, it is advisable to continue your current education rather than transferring out of your current college without completing your degree. The skills learned in a traditional college setting are often invaluable, and they will make you all the more well rounded and marketable.