no, dear, 'acaba' means something like 'I wonder if..', but there's not exactly matching word in english about it.
('they are similar' is in the part I edited in my previous message.)
In order to be sure (for you and Bilal), here goes the source text with the right spelling:
"Dün yine aklımdaydın. Saatlerce tıkandı boğazıma, ağlayamadım. Acaba, sensizlik mi, yoksa ölüm mü daha korkunçtu ayırt edemedim, ikisinin de farkı yoktu birbirinden. ölüm, sensizlik (demek)ise, sensiz zaten ölüyüm diye düşündüm."
and here goes the bridge:
"You were in my thoughts yesterday,again. For hours the tears were in my throat, I couldn't cry.I wonder, if the Death or being without you is more fearful, I could´t see any difference, they're similar.
If being without you was Death then I'm already dead, I thought."