What can i do about constant anxiety and nervousness?

Make an appointment: Your description of constant anxiety, warrants consultation with a mental health professional (psychiatrist, psychotherapist), they may be able to give you strategies to cope and medications to reduce your suffering. Go see them and good luck!

Stay active: Exercise is a great way to relieve stress. Your body releases endorphins during exercise, which can help you feel calm. If you exercise 30 - 60 minutes a day, your stress levels can improve. When stressed, take 5 slow, deep breaths with your eyes closed, then roll your shoulders forward 5 times, then back 5 times. This will slow your heart rate and release tension in your neck and shoulders.

Multiple ways: Some things you can do on your own: meditation, yoga, tai chi, breathing exercises, etc. Stop all stimulants (caffeine, etc). Others require professional help. If your anxiety is "constant" it merits evaluation by your doctor. Many conditions can create or exacerbate anxiety, including medications. If all this is clear, a psychiatrist or psychotherapist can help with more focused treatments.