under the weather
• slightly unwell or in low spirits.
• "she was sufficiently under the weather to have to pull out of the championship"
Similar:
ill,
unwell,
indisposed,
ailing,
poorly,
not (very) well,
not oneself,
not in good shape,
out of sorts,
not up to par,
under/below par,
peaky,
liverish,
sick,
queasy,
nauseous,
off colour,
not up to snuff,
funny,
peculiar,
crummy,
lousy,
rough,
ropy,
grotty,
wabbit,
crook,
queer,
seedy,
