Hi there ~
I understand your concerns. Your sleep problems and insomnia
may be related to both being on ADHD
medications as well as having the popping sensation, the reason for which you need to look into, by visiting with doctor. It might turn out that the popping sensation was serious and you might have to take yourself to a neuropsychiatrist if that is recommended. I would think that the doctor would order detailed imaging studies of your head and neck after a thorough history and physical examination, as well as labwork. I hope this helps.
Take care and have a lovely day!