I echo Ken's advice - it is important to figure out what you ultimately want to do before you start making changes. The ease with which you can switch from one science major to another likely depends on the school you attend - the best place to start is your academic adviser or a trusted professor.
I think the most pragmatic way to think about your career aspirations is to backwards plan. Identify careers you think you would be interested in and work back to find a program that allows you to pursue multiple career interests. For example, if I think I might want to work at a think tank doing research but also am considering consulting for a professional services firm, I might pursue something like economics or math. Both of those majors would provide tremendous technical skills that are extremely attractive to employers and are well-suited for a wide range of career options. The science program you are in now may fit with some of your career interests or you may find that you do need to investigate the possibility of making a change. It's important to step back and analyze whether you are on the right path.
I linked a career guide below and HIGHLY recommend you read the entire thing. I know it is long, but I can't overstate how beneficial I think it is. Read a section a day and you will finish in no time. The research is very interesting and it's very well written.
Jacob recommends the following next steps: