Insight needed

Ok, so I have known that I have adhd since I was evaluated at age 17. I never took my medication but now that I’m 35 I wanted to really try it out to see if it will help, as I’ve truly been struggling. My doctor started me off on 10mg vyvanse. It helped a little but to be honest didn’t notice much of a difference. She was hesitant to up my dose but eventually did at 20mg. Again that felt a bit better but was not lasting long or really getting positive effects from it for more than a couple hours at a time. I stayed here for a while but eventually she did bump it to 30 but basically told me she wouldn’t go higher because it’s telling her that my body just doesn’t work well with it. I am on 30mg now and it helps me a ton but only for about 3 maybe 4 hours and then I crash quite a bit. Is this just not the right medication for me? I take it how I’m supposed to and avoid vitamin c. Not sure if I’m missing something else