why do I have such bad anxiety when I am trying to go to bed at night?

Anxiety is a very common problem encountered both by primary care physicians and mental health professionals. Just as you say, patients will often be able to deal with their anxiety during the day as a result of focusing on other tasks such as work or school. However, many patients will suffer at night as the daytime stimuli are no longer present. The best advice for you would be to seek out the care of your primary care physician. He or she can talk to you about the different stressors in your life and healthy ways to cope with these issues. If needed, you can be referred to a mental health professional such as a psychologist or psychiatrist for more specialized care. Many patients with anxiety find a great amount of relief through therapy and counseling sessions. For those patients that continue to have problems, medication can help. There are a number of medications called anxiolytics (i.e., medications that "break up anxiety") that can help ease the mind and help you to obtain a healthy amount of sleep at night. You should talk with your doctor about these medications, the side effects (such as the potential to cause daytime drowsiness), and if they might be appropriate in your situation.