Quote: "I started feeling like nothing matters, feeling really distant, asking questions about reality etc...."
I have had situational anxiety since the age of 16. I recently went through a stressful event relating to a friend dying. I remember having really bad nightmares and waking up not only myself but my husband in the process.
We sat up and all of these things I had not consciously been aware of came flowing out of me such as "When I am gone, I will not have made a difference in the world. I just take up space and am not contributing to anything. I will probably go soon because there is no reason for me to be on Earth."
My husband was able to talk me through and calm me down so that I could get back to sleep. The next day we talked more and I discovered that the situation (in your case college finals) was what had brought all of these negative and questioning feelings on me. Once I discovered the cause which was fear of my own mortality (my friend was very giving and helped a lot of people in her life) and my fear of not living up to my image of her, I was able to begin to calm down and things got back to normal.
I think it is very helpful to have others that can see outside of you and give you an anchor to help understand your anxiety feelings and fears. Do you have a close friend or family member who you can talk to?