Are you taking just the regular immediate release? If so, maybe you need to try an extended release such as Concerta or Vyvanse. I have found with Vyvanse that the crash is less than any other med I have taken. As far as the teeth clenching, this has been a big problem for me. If it continues, as it has for me, you will start experiencing a lot of pain in your jaw, neck muscles, and teeth. From what I have read, this side effect may or may not go away. I believe mine is being caused by my Prozac and it has not gone away 3 weeks into the Prozac. I am also on Vyvanse but it stated after I started the Prozac and before I started the Vyvanse. Anyway, I would recommend you switch to extended release meds to lessen the crash and you start at a very low dose and work your way up. It takes a while to get ADHD meds sorted but is worth it when you get there. Good luck.