Hello,
Thanks for posting your query.
The condition you are suffering from is called Sialorrhea.
It can have varied causes like tonsillitis , adenoid hypertrophy , salivary gland inflammation , medication sideffects to serious causes like tumours , neuromuscular disorders etc .
In order to be able to guide you better and come to the most probable diagnosis kindly provide details about your problem , like ,
1. Onset duration and progress of your problem ( recent or long standing )?
2. Any other associated symptom Sinusitis , acid reflux , fever , oral ulcer etc?
3. Any past medical illness or any medicines you are taking for any current illness ?
4. whether you have been examined and investigated for the same by a doctor ?

I assume that you have no significant illnesses and considering your age the most probable cause does seem to be a inflammatory enlargement of adenoids or salivary glands causing this problem . In that case the best step would be to get yourself evaluated by a Oral or ENT surgeon ( otolaryngologist ) to get a confirmed diagnosis so that appropriate treatment can be started .
The doctor might start you on anticholinergic medicines like glycopyrrolate or scopolamine to provide some relief .
In case there is any more information you need to share please feel free to do so.
Hope I have answered your query.
I'll be available for follow up queries.
In case you have no further queries kindly accept my answer to close the query .
Awaiting your response,
Regards

---