Hey I've been of High school for at least 2 weeks cause I've not been well... am I missing out on stuff... am I falling behind?

This is a question for your teachers as we do not know your work load.

Didn't teachers give you or your parent(s) some work to do at home to help keep up? If not, ask for some.
Teachers usually consider how much someone has been out sick when exam time comes. But only so much, depending on how ill you are, so try to read and work on problems in textbooks and find out what's going on in each class.

OK thanks