The details you have given here are insufficient to make a diagnosis. If your condition has been going on for sometime. Please consult your general physician and take help from a Psychotherapist.
There may be multiple reasons for anxiety and sleeplessness. Seeking help now can control the problems and help you manage the condition before it worsens. This is a common problem and not something that a GP or Psychotherapist cannot help you with.
Taking help at the right time is important.
The chain of thoughts and emotions related to sleep that you have mentioned are common factors responsible for sleeplessness. Insomnia or sleeplessness generally arises due to racing thoughts that occupy the mind during sleeping time. These thoughts are generally trivial in nature, which means they are irrelevant to any important task at hand and just make the mind wander aimlessly. Sometimes there may be some important unresolved issues happened during the day may preoccupy the mind. This is generally experienced as negative thoughts and worrisome.
Worries are carriers of anxiety. So what you need to do is stop worrying while going for sleep. This is done by shifting your focus from thoughts and worries to sleep. You focus too much attention on your content of thoughts which is obviously negative. This makes you feel anxious and occupied. Unless you get rid of this anxiety, you cant go to sleep. That's what your mind tells you.
But you can train your mind to go to sleep instead of focusing on worries. This is done by focusing your mind on the need and feel to take good sleep. Just fill your mind with thoughts that how important it is for you to sleep. Visualize yourself sleeping and how calm or relaxing it feels when you sleep. Feel the comfort and peace of sleep by imagining about it. This will help you to feel sleepy and make sleeping easier for you. Mind has the power to make you feel the way you want. So use this exercise to let your mind stop wandering and worrying and guide you to sleep.
You can search for similar guided imagery exercises for insomnia on google. They will provide you a script and a step by step procedure to help you fall asleep.
All the best.
Try Guided Imagery exercises for Insomnia. These are self-help techniques that anyone can do at home on their own.
If you are unable to do the exercise yourself, then consult a psychologist. Don't go for medicines as they will not give you the ability to regulate your sleep habits.
Negative thoughts & fear are hard to face and get harder when they start affecting sleep. It is a negative & disruptive cycle you have been going through.
There could be physiological or psychological factors acting behind your anxiety. Through the way you have mentioned it, I am interpreting that you start with negative thoughts, which when intensified leads to fear followed by emotional reaction in your body which disturb your sleep and disturbed sleep leads to more anxiety.
Short term solution would be to try and stop the flow of thoughts once you are aware of them however if they intensify and lead to bodily/ emotional discomfort, you will have to try different ways of soothing your bodily sensations and emotions such as relaxation techniques, soothing music, taking a shower, taking a walk etc. Medicine may come handy here.
Long term solution would be to make an effort to understand the cause & tackle it rather than trying to address symptoms. Your negative thoughts, fear and anxiety have been arising from within you as a response to situations or otherwise. Stand up & address every thought or every fear for which a professional(psychiatrist, psychologist) could be of assistance.
Hope you start taking control of your life and addressing the issues soon. Take Care.
Rule out the Physiological source of Disturbance followed by Taking Measures to address Psychological Functioning