The possibilities of the diagnosis are;
1) Obstructive sleep apnea (OSA).
2) Gastroesophageal reflux disease (GERD)
3) Allergy; medications may be a reason, but you may need an allergy test (this is nowadays done by the blood; termed as in vitro allergy test).
Obstructive sleep apnea will require following investigations;
A) a sleep study, preferably polysomnography
B) lateral cephalometry,
E) computed tomography (CT) scanning,
GERD can be diagnosed by;
a) An endoscopy
b) 24 hours pH estimation of esophagus.
Please feel free for your follow up questions.
I would be happy to assist you further, if you need any more information.
Thanks for using Just Answer.