I feel like someone is chasing me. What can I do?

Evaluate. Sounds scary. Ask your primary care doc to refer you to a psychiatrist so the underlying causes can be determined and addressed.
Get professional hlp. There can be any number of reasons you feel that way. Don't wait , talk to your physician or a mental health professional. You may have enough discomfort that sharing it with family or friends is difficult. A professional is not likely to dimiss it as nothing and will check it out with you. Family and friends may be tempted to make light of it, possibly delaying help.