Usage limits change

So for a while now I have been creating notes using lectures from my professor at my medical university to study for an exam. For the past 3 weeks i have been using sonnet 4.6 max and i was able to get 4-6 topics per day with the pro plan. Since 3 days ago, each topic takes around 45-50% of my usage limit. So 1-2 topics per session max which has brought down my pace. Did the limits change? Should i continue using max or go to high? Also what will happen if I switch to sonnet 5? will i lose the progress of t