Is this fear and anxiety is only during the night or you normally face this Anxiety? !!
Whatever it is there is always a reason to develop a pattern in us.
Hence to identify and to handle it in the normal course of life, I suggest you to Consult a Psychologist /Counsellor in your city.
If the anxiety & fear occurs only at sleep time, the reason for the same needs to be analysed. This may occur if you have suffered frequent panic attacks at night time, in which you anticipate them & get anxious beforehand. If you are anxious throughout the day, then assessment for anxiety disorder needs to be done. One your anxiety is taken care of, hopefully your sleep should improve as our body needs relaxed mind & body to sleep.
You will need to visit a mental health professional.Till then you can practise relaxation techniques & deep breathing to calm yourself .