This is because of bad oral hygiene, you must have tartar or plague accumulated around the tooth which is infecting your gums as well as tooth
The treatment may be
1 Scaling and polishing (normal cleaning)
2 Curretage and root planning (in severe case :deep cleaning )
Followed by maintenance therapy till the problem subsides
Next Steps
Visit your dentist for proper clinical and radio graphical examination to determine the proper treatment plan
Health Tips
Maintain oral hygiene (brush twice )
Use good quality soft tooth brush and also a plastic tongue cleaner
Use of mouthwash (chlorhex in 1:1 ratio normal water:mouthwash) will help