I’m not feeling well/ under the weather/ sick as a dog.I am not feeling myself
I am feeling a bit off colour; .

I feel a little out of sorts ; I feel a bit funny.

I've got the flu/one heck of a cold/ a wog.
I feel like the pits, my throat is killing me, my nose won't stop running, I've used a million tissues, my head feels twice its size.

call in sick
“I’m indisposed,”
“I’m not able to really go to work today, or really show up.”

catch the flu /get a cold
have a fever / get a temperature/

have a body ache
it’s a pain that pulsates, that throbs.

have a stuffy nose
have a runny nose= the sniffles
have to blow your nose

you cough, you sneeze, you vomit, you throw up and you puke.

barf / chuck up /  come up / heave / hurl / spew / 

bilious / bloated / bring up / disgust / nausea / queasy / upset

have diarrhea=have the runs