No need for 'fy hun(an)' here as the 'ym-' implies that the action is a reflexive one.
Dw i'n golchi'r llestri - I am washing the dishes
Dw i'n ymolchi - I am washing myself
Thanks, I was about to ask that!
Does anyone know where the "fy hun" came from?
So if I want to say I've washed...?