I had operation of the tooth last week but...

Treatment of bad breath :
The treatment depends on the cause of the occurrence of bad breath and until the diagnosis is made after some necessary medical tests , I advise you to maintain dental hygiene on a daily basis , such as using a medical paste such as Sensodyne . You should also avoid smoking and avoid carbonated drinks . In addition, you should make sure to drink natural juices such as lemon and mint with drinking a good amount of water daily, from 2-3 liters while avoiding unhealthy food, fast food. In case of dental infections: Oracure gel twice a day with Septoral Mouth wash treatment twice a day for 5 days .
Causes of bad breath :

• Many reasons may lead to bad breath such as:
• Dental infections .
• Tooth decay .
• Esophageal reflux .
• Unhealthy meals .
• Infections of the paranasal sinuses .
• Smoking .
• Other reasons .

Necessary medical examinations in case your problem persists :
A complete blood test with a dental examination for infections , and an imaging scan of the paranasal sinuses in case of sinus infections or swelling that cause bad smell . It can also be made 
Esophagogastroduodenoscopy for inflammatory conditions and Gerd.
Advice :
Follow-up with a specialist oral and dental doctor .