Translation Catullus 50: verses 14-21

But my exhausted members by this labor afterwards,

half dead were lying on my bed,

I did for you this poem, my dear,

from which you might gather my pain.

Now beware to be bold, and beware, my dear,

to spit on my begs, we pray you,

so that Nemesis would not demand a punishment for you;

this is a violent goddess: beware to not hurt her.
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Emilie, you clearly understood the Latin, but the English is a bit awkward; I've rephrased it below:
 
but afterwards my limbs, worn out by labor,
were lying half dead on the little bed,
I made this poem for you, my dear,
from which you might gather my pain.
Now beware to be bold and, I beg, beware
to spurn my prayers, my sweet,
lest Nemesis demand a punishment from you:
she is a violent goddess:  beware to hurt her.