I'm not feeling well today.

not for all the tea in China

not by a long chalk/stretch

to not eat something

It is not what I am looking for.

I’m not losing any sleep over that

Do not make so much fuss!

not by a long shot

Do not fuss!

Not getting the job turned out to be a blessing in disguise

to not even begin to try

It is not quite the thing.

not to know much about something

not to be worth a straw

Do not make so much ceremony!

not worth a straw

not by any stretch of the imagination

not to feel up to the mark

I'm not worried about it.

not to have a bloody idea about anything

Not right now!

I'm not a good listener.

not to have a bloody clue about anything

not a big deal

not everyone’s cup of tea/not everyone’s money