Last weekend I went camping with my cousin who threw up 3 times. Now, I am throwing up constantly. What could it be?

Virus. You most likely contracted a virus...A stomach bug. Sounds like your cousin had it and you got the same thing. Sip room temperature fluids often. If you are unable to keep down anything and are feeling weak, you need to be seen. There are some great homeopathic remedies that can help as well.