Bad breath can be due to number of reasons
Dental caries, plaque/ calculus , any respiratory problem.
You have to get it diagnosed properly so please visit your nearby dentist.
Sensosdyne do help in some cases but not all, your dentist will check and recommend the paste good for You.
Next Steps
visit as early as possible to dentist,,so that the condition doesn't detiorate further, "a stitch in time saves nine"
Health Tips
brush twice and rinse after every meal