Wears off quickly?

Hi, I started on Vyvanse generic 30mg about 3 weeks ago. I’m a 38 year old female. It is life changing for me. Calms my mind so much, helps me get motivated and focus. The problem is that it wears off about 1-2pm and brain fog set in. Will a higher dose last longer or does the dose not matter when it comes to duration? Of course I’ll ask at my next appointment but just wondering what your experience has been.