Yup, usually low tone meowing selalunya la indicating cat in distress or in pain. I think you ever heard a sick cat meowing. I believe you know that cat is best at hiding their sickness, whatever happens, they'll show you when only you realized it is too late.
I suffered some lost this month for mange and fever. Today diaorg seronok je main, manja manja, ulik ulik muka. Esok, terbaring, tercungap cungap. This is very hard for me, and I believed that I have no more tears to cry for if I lost a cat. So, I pray for the best for you and your cat.