It's really difficult for a lot of people, after graduation, and facing major life changes. Just do your best to push through with the job and internship search; keeping busy will help with keeping your mind off things. You have goals and things to look forward to, like grad school- are you going in the fall, or are you going to be applying to grad schools in the fall? If the former, you can look forward to that; if the latter, you can put your energy now into that hunt. If you're not thrilled with your major and your life path, you're very young, and there's still plenty of time to change, either through getting into the workforce and gradually making sidelong moves, or through seeking a different program in grad school.

I hope you have family or friends to talk to about this- or here on the boards. Do your best to take care of yourself, seek support, and keeping moving forward.