Vyvanse tolerance?

Hey everyone! I'm wondering what others have experienced when they first started taking Vyvanse. I got my diagnosis and started medication in April. We started with 20mg in the morning everyday for two weeks, then increased to 30mg everyday in the morning as well. The first two weeks went well I would start to crash around 8-9pm but feel fine by 9:30-10pm. The first two weeks of the 30 mg went well and the side effects (mostly nausea because of my sensitive stomach) wore off however over the last 10 days or so I noticed it just doesn't kick in at all like it truly feels like I never took it.

I do have an appointment coming up with my dr to discuss how the first 1.5 months have gone, I'll bring up these concerns but I'm also wondering is there any other info I should bring up or questions that might help? And has anyone else experienced this in the past? TIA