It is indeed disturbing that your job has undergone such a drastic change and that too for worse. Finding a job that you love is hard to find and once you have that job it is important to retain that job at all costs. The problem you have mentioned is indeed complex as dealing with a problematic manager is a sensitive issue and one needs to be approach the issue carefully. However, it is possible to deal with the issue at hand but first you need to evaluate yourself.
As you have mentioned, the old manager was very lenient, you need to assess whether the new manager is actually being difficult or is it your perceptions since being forced to follow a routine can be tough if you are not used to it. It might be that the new manager is trying to bring about a change in the office discipline which can in long term improve the quality of work. Moreover, try to see if there are any discrepancies or problems in your work so that you can work on them. Self evaluation can help you in improving your performance and making sure that there is nothing lacking from your end.
If however, you are convinced that the fault lies at the manager’s end, it is best to talk to him. You can tell him that this certain policy is affecting your productivity negatively and hopefully something can be done to make it more acceptable. In all probability, the manager will work on that as he is primarily interested in increasing productivity of the employees.
Worst case scenario, the manager is totally unprofessional and holds a grudge; you can report his behavior to the HR or higher authorities. Make sure you have actual incidents of unprofessionalism at his hand which affects the company. Ask your colleagues how they feel about the new manager and take them on board if you are planning on filing a report.
We hope that you are able to sort the problem and continue the job you love.