It seems like this is the be-all-end-all moment of your life -- the time that you need to choose how you want to spend the rest of your time and what you want to spend it doing. This decision can cause anxiety in everyone, even if you're one of those people who's had the same train of thought since they were 5 and were asked, "What do you want to be when you grow up?" The sheer number of majors and jobs that you know nothing about do nothing to lessen the impact of this decision for you.
A lot of people give advice about doing what makes the most money or doing what you love, but sometimes neither of those options are the best for you, and that's OK. It is OK not to know what you love to do enough that you want to do it every day. It is OK to be indecisive about this. If you change your major several times, it is still OK. This is what you want to do, and while others can help you make a decision to a point, it is still up to you to decide what to do, and that is a hard decision to make.
While it may feel like you have no time to make a decision, you have all the time that you need. Even if it means you have to graduate a bit late or won't follow the plan that you're hoping for or have to take some summer classes to get it all done, then that is for your benefit and betterment and it means that you are truly dedicated to what you're planning on doing. If this is something that you really want to do it is up to you to choose that and to do what it takes. While this may seem scary, all of your hard work will pay off later.
A huge worry of mine when it comes to choosing a major is the job market, but that in itself is something that you should not worry about because it isn't something you can't control. Maybe the economy is terrible and maybe the job you want isn't looking too great, but if you love what you want to do, then it will show when you're trying to get a job, and your passion for what you're doing will be what gets you on for that internship or job or residency.
In spite of your fears and worries about all of this, take a few minutes to think about your major and what you wish you could do as a career both within your major and with a different one. If you're deciding between two things, take a coin, assign heads and tails to whatever you like, and flip it. If you're happy about what it lands on, go with it and live a happy life. If you wish that you had gotten the other side and could flip again, then that should tell you what your gut wants you to do.
