Antidepressants tablets

This is my second day that I am having antidepressants tablets. I have totake one tablet 20gm a day.last night I did not sleep well. I rang my nurse this morning about not sleeping well last night. She advised me that I should Chang the time to take the tablet. And she said you would get some of the side effects first week but second week you would get good effects. I have to take a day off from work as I do not feel well because of less sleep.