Since you had antibiotics for 10 days your bacterial flora in the intestine may be affected which helps in the re absorption of water from the stools. So what you can try is stop codeine and take some probiotics available in your home or you can get it from your family doctor. Since you dont have fever or abdominal pain
this is usually non infective diarrhoea
induced by the antibiotics. Hence, whenever you take antibiotics for any reason next time take some probiotics containing lactobacillus
spores alongwith the antibiotics.