Changes in daily routine are probably one of the most common causes of constipation. This is because the intestines have a sort of internal clock that regulates when bowel movements occur. If, because of changes to your work or school schedule, your clock and your intestines' clock are no longer on the same time, constipation can certainly result!
Fortunately, this is a problem that is likely to correct itself over a period of a few weeks. However, there are several things you can do to help out with the symptoms in the meantime. First, make sure you drink plenty of water and other liquids, as being dehydrated (as sometimes occurs with a new job or busy school schedule) doesn't help the constipation. Also, make sure to eat regular meals heavy on the fresh fruits and vegetables (to increase your fiber intake).
While things are getting sorted out, you may need to take a daily medication to help you have bowel movements. In addition to senna (Ex-lax being one form of senna) another great medication is Miralax (polyethylene glycol), which is also available over the counter.
If your symptoms continue, I would recommend seeing your primary care doctor
to help develop a more effective treatment plan.