I am in my 17th week of pregnancy. I work in a pub with a schedule of ...

To start, you should speak with your employer and discuss your situation with them. Your employer might be willing to assign you to lighter duties or alter your work schedule. However, the decision to transfer to lighter duties and change the work schedule depends on the company's policy and the legislation of your country. If you bring a medical certificate from the hospital, your employer may consider transferring you to lighter duties or changing your work schedule. However, this does not guarantee that your night shifts will be eliminated. Your employer might offer you other work options or schedules. Regarding shift workers, they may continue to work night shifts if it is necessary for the operation of the pub. However, your employer might find other solutions to this problem, such as hiring additional staff or changing the shift workers' schedules. In any case, it is important to discuss this situation with your employer and find a solution together that is satisfactory for all parties.

You need to go to your job and clarify things there, not here.

Ask your boss, only they can answer your questions.