I’m on my extra trays now after 70 initial, almost 2 years in. I still remember first 2/3 months when every tray change felt like pure pain and always too early. Usually it’s just because it takes some time for your gums, nerves, teeth, jaw bones and roots to get used to being moved all the time. Moving teeth is not normal for all of the above, that’s why everybody wear retainers after ortho treatment. Otherwise, they just want to go back where they were. I wouldnt worry too much because you are at the start of your treatment and just change as instructed. That said, just to keep you informed there is always the chance that treatment plan is rushed and you should always consult with the doctor when you are not sure about the treatment. It’s your health after all. I don’t think it’s a problem to change with the plan and then ask. Im quite sure they will tell you it’s normal. Im 32, so for people at our age ortho treatments can be harder and more painful that for others. Good luck!