I agree with the optician on one aspect. If your reading vision is good, then the problem is not with your eyes. It is with your glasses.
There are three things that come to mind. One is that progressive lenses require more time to adjust to (especially if it is your first pair like that). It appears to me though that you have given it enough time (2-3 weeks).
Second, maybe the doctor mismeasured your distance prescription.
That leaves one thing. Progressive lenses require much stricter measurements than regular single vision lenses. If the optical zone is not in the right place (this is the spot on the lens that your eyes are actually looking through), if the pupillary distance measurement is not right (this is the distance between your pupils), if the segment height is not right (this is the position of where the near vision starts), if the channel is not wide enough, then you may have problems regardless of what you do.
To work through it logically, you should ask the doctor to remeasure you prescription to see if it is correct. If so, you should ask them to check the prescription on the lenses to see if it is the same as the prescription for your eyes. Finally, if everything else is correct, they need to remeasure the lenses themselves (optical zone, pupillary distance and segment height).
Hope this helps and good luck.