I have the flu and I don't want to miss cl?

I felt like hell on sunday, I threw up yesterday and stayed home slept all day, Today I feel better but I am coughing and expelling phlegm on top of that every time I cough hard I get a head rush. I don't want to miss cl I have trigonometry & macro-economics today but I don't know if I should go and cough up the phlegm. School just started last week I don't really want to miss a day already