I Have a Question

When I take the cough syrup from the doc, it will put me to sleep. The cough syrup has finished. Now I'm taking a cough syrup from a pharmacy store. Is it save to take otc cough syrup each time I wake up (1 table spoon) so that I can sleep. I wake up 3-4 times at night becoz of the cough. This means I will take 3-4 table spoon of the cough syrup. I know the cough syrup at the store is milder than the cough syrup from the doc. Thank you for your advise.