I fell ill = 我生病了 I'm still sick = I haven't recovered yet = 我身体还没恢复好。

我还在生着病。

you can translate “still” to “仍然”

you can translate “still” to “仍然”

还 is someone or something still in the middle of a condition and not end yet. So when you use 还 normally you don't use 了 in the same sentence. I am still sick.（not recovery） 我还在生着病。（没有康复） I am still in love with her. 我还爱着她。 还+verb+着 is a little bit like present progressive 了 normally is used in a sentence in past tense.