What Causes Sleeplessness After Taking Noliprel Forte?

I got a Tonsillectomy done 2 days ago. I am taking Asterfor 500mg for 4 days. Trometamol 25mg. I took Narapel Forte(codine) for two days but apparently it caused me insomnia and I have not been able to sleep since surgery. My doctor suggeste taking Cataflam instead. What can I do to get rest? Also it seems when I try to rest phlegm in my throat causes me to not fall asleep. Do you have any other suggestions